📌 How to Use
First read the questions carefully using the Read section. Use the Details button to understand concepts clearly. After completing reading, click Practice Quiz to test yourself.
📘 Study MCQs
Q1. A student is having difficulty reading the blackboard from the back of the class but can read a book clearly. Which defect might they have?
• Hypermetropia
• Presbyopia
• Myopia
• Astigmatism
Answer: Myopia
Myopia (nearsightedness) makes distant objects blurry while nearby objects remain clear, explaining difficulty seeing the board.
Q2. Why are the lenses of diving goggles curved and not flat?
• For better style
• To correct vision underwater
• To counteract the refraction of light in water
• To prevent water pressure damage
Answer: To counteract the refraction of light in water
Water refracts light differently than air. Curved lenses help compensate for this refraction, allowing objects to appear in their correct position.
Q3. A truck driver prefers to use yellow-tinted glasses at night. Why might this help?
• Yellow light is brighter
• Yellow filters reduce glare from headlights
• Yellow light scatters less in fog
• Both B and C
Answer: Both B and C
Yellow light reduces the scattering of bright oncoming headlights (glare) and penetrates fog better than white light, improving contrast and visibility.
Q4. Why do traffic stop signs use red as the primary colour?
• Red is a bright colour
• Red light scatters the least and travels farthest
• Red is easy to paint
• It’s an international standard
Answer: Red light scatters the least and travels farthest
Red light has the longest wavelength and is scattered the least by atmospheric particles. This allows the signal to be visible from the greatest distance, even in hazy conditions.
Q5. A fisherman sees a fish in the water. To spear it accurately, should he aim directly at the fish, above it, or below it?
• Directly at the fish
• Above where the fish appears
• Below where the fish appears
• To the side of the fish
Answer: Below where the fish appears
Due to refraction, light from the fish bends as it leaves the water, making the fish appear shallower (higher) than it actually is. Aiming below compensates for this.
Q6. Why do many emergency vehicles (like ambulances) often have the word “AMBULANCE” written in reverse on the front?
• For decoration
• So drivers can read it correctly in their rear-view mirror
• It’s a mistake
• To confuse other drivers
Answer: So drivers can read it correctly in their rear-view mirror
The reverse writing appears correct when viewed in a rear-view mirror, allowing drivers ahead to quickly identify an emergency vehicle approaching from behind.
Q7. An elderly person needs to hold a menu at arm’s length to read it clearly. What is the most likely reason?
• Myopia
• Hypermetropia
• Presbyopia
• Cataract
Answer: Presbyopia
Presbyopia is the age-related loss of the eye’s ability to focus on near objects. Holding reading material farther away helps bring it into focus.
Q8. Why are car headlights designed with a parabolic (curved) reflector behind the bulb?
• To make the car look good
• To produce a parallel beam of light that travels far
• To scatter the light in all directions
• To change the colour of the light
Answer: To produce a parallel beam of light that travels far
The parabolic shape reflects light from the bulb into a strong, parallel beam, maximizing illumination of the road ahead without wasting light upwards or sideways.
Q9. Why does a pencil look bent when placed in a glass of water?
• Due to reflection
• Due to dispersion
• Due to refraction
• Due to scattering
Answer: Due to refraction
Light rays from the submerged part of the pencil bend as they pass from water (denser) to air (rarer), making the pencil appear bent at the water’s surface.
Q10. A person who works long hours on a computer frequently experiences eye strain. What is a simple practice to reduce this?
• Wear sunglasses indoors
• Look at distant objects periodically
• Use a brighter screen
• Keep eyes very close to the screen
Answer: Look at distant objects periodically
Continuously focusing on a nearby screen tires the ciliary muscles. The “20-20-20 rule” (look 20 feet away for 20 seconds every 20 minutes) helps relax these muscles, reducing strain.
Q11. Why are safety goggles important for someone working with welding equipment?
• To look professional
• The intense UV and bright light can damage the retina
• To keep dust out of the eyes
• All of the above
Answer: The intense UV and bright light can damage the retina
Welding produces extremely bright light and harmful ultraviolet radiation. Goggles with special filters protect the retina from permanent damage (e.g., “welder’s flash”).
Q12. Why do we often see a “glint” or bright spot in a person’s eye in a photograph?
• The camera flash is reflecting off the retina
• The camera flash is reflecting off the cornea
• It’s a sign of good health
• The eye is producing light
Answer: The camera flash is reflecting off the cornea
The smooth, moist surface of the cornea acts like a convex mirror. Light from the camera flash reflects directly back into the lens, creating a bright white spot.
Q13. Why does the sun look much larger near the horizon at sunrise/sunset than at noon?
• It is physically closer to Earth
• Due to an optical illusion comparing it to trees/buildings
• Atmospheric refraction magnifies it
• Scattering makes it look bigger
Answer: Due to an optical illusion comparing it to trees/buildings
When the sun is near the horizon, our brain has familiar objects (like trees) to compare it to, making it appear larger. This is called the “moon illusion” (it also applies to the sun).
Q14. Why are concave mirrors used in makeup/shaving mirrors?
• They make the face appear smaller
• They produce an enlarged, upright virtual image when the object is close
• They produce real images
• They are cheaper
Answer: They produce an enlarged, upright virtual image when the object is close
When the face is placed within the focal length of a concave mirror, it creates a magnified and upright virtual image, useful for seeing fine details.
Q15. After being in a dark movie theater, why is it hard to see when you first walk out into bright sunlight?
• The pupils are wide open and need time to contract
• The cones in your eyes are not working
• You have temporary blindness
• The sun is too bright for anyone
Answer: The pupils are wide open and need time to contract
In the dark theater, your pupils dilated to let in more light. Stepping into bright light overwhelms the retina until the iris muscles contract to make the pupil smaller (this takes a few seconds).
Q16. Why do wet roads sometimes appear darker than dry roads?
• Water changes the road’s colour
• Water absorbs more light
• Water creates a smooth surface that reflects light specularly (like a mirror) away from you
• Water evaporates and cools the road
Answer: Water creates a smooth surface that reflects light specularly (like a mirror) away from you
A dry road is rough and scatters light in all directions, including towards your eyes. A wet road is smoother, so it reflects light more like a mirror, sending the light from streetlamps or the sky away from you, making the road look darker.
Q17. Why do we blink our eyes?
• It’s a nervous habit
• To spread tears and keep the cornea clean and moist
• To help focus
• To exercise eye muscles
Answer: To spread tears and keep the cornea clean and moist
Blinking spreads a fresh layer of tear film over the cornea. This keeps it transparent, provides oxygen, washes away dust, and ensures smooth light refraction.
Q18. A lifeguard at a pool is trying to locate a struggling swimmer at night. Why might it be harder to see them under pool lights?
• The water scatters the light, creating glare
• Swimmers are too fast
• The water absorbs all light
• Pool lights are not bright enough
Answer: The water scatters the light, creating glare
Light from underwater pool lamps is scattered by tiny particles and water molecules (Tyndall Effect). This creates a bright, hazy volume of light that can obscure objects (like a swimmer) within it.
Q19. A person with normal vision gets reading glasses. What will happen if they try to look at a distant mountain while wearing them?
• The mountain will look clearer
• The mountain will look blurry
• Nothing will change
• The mountain will look upside down
Answer: The mountain will look blurry
Reading glasses are convex lenses meant for near vision. They add extra converging power, making distant objects focus in front of the retina, causing blurriness (similar to induced myopia).
Q20. Why are periscopes in submarines often use a combination of prisms instead of mirrors?
• Prisms are cheaper
• Prisms provide total internal reflection, which is more efficient than mirror reflection
• Mirrors rust underwater
• Prisms are lighter
Answer: Prisms provide total internal reflection, which is more efficient than mirror reflection
Mirrors can have imperfect reflection (some light is absorbed). Prisms use total internal reflection, which reflects 100% of the light, providing a brighter and clearer image.
Q21. Why are high-quality cameras and telescopes often have very large lenses or mirrors?
• To make them look impressive
• To gather more light for a brighter, clearer image
• To make them heavier and stable
• To increase the magnification only
Answer: To gather more light for a brighter, clearer image
A larger aperture (lens/mirror diameter) collects more light from a faint object (like a distant star). This results in a brighter image with more detail, crucial for astronomy and low-light photography.
Q22. Why does a cut diamond sparkle with different colours?
• It emits its own light
• Due to total internal reflection and dispersion
• It has coloured paints inside
• Due to scattering from impurities
Answer: Due to total internal reflection and dispersion
A diamond is cut with specific angles. Light entering undergoes multiple total internal reflections. During these reflections, dispersion occurs, splitting white light into its spectral colours, which then exit at different points, creating “fire” or sparkle.
Q23. A person feels their eyes are dry and vision is slightly blurry after a long flight. What is a likely cause?
• Cabin pressure changes eye shape
• The very low humidity in the airplane cabin evaporates tears quickly
• High altitude affects the retina
• Food served on the plane
Answer: The very low humidity in the airplane cabin evaporates tears quickly
Airplane cabins have extremely low humidity. This causes the tear film on the cornea to evaporate faster than it’s replenished, leading to dry eyes, discomfort, and temporary blurred vision.
Q24. Why are blue or green screens used in movie special effects (chroma key)?
• They are calming colours
• They are colours least like human skin tones
• They are the most common paint colours
• They reflect the most light
Answer: They are colours least like human skin tones
Blue and green are chosen because they are distinctly different from common skin tones and clothing colours. This makes it easy for software to isolate and replace that coloured background with any other image.
Q25. A rainbow is always seen with the sun behind you. Why?
• The rainbow needs sunlight to illuminate the rain
• The rainbow is a reflection of the sun
• The light must be refracted and reflected back towards you by raindrops
• It’s just a coincidence
Answer: The light must be refracted and reflected back towards you by raindrops
A rainbow forms when sunlight enters a raindrop, refracts, reflects off the inside back surface, and refracts again as it exits. This specific path sends the dispersed light back towards the sun’s opposite direction, which is where you are standing.
Q26. Why do streetlights often appear to have a starburst or halo effect in a rainy photograph?
• The camera lens is dirty
• Droplets on the camera lens scatter the light
• It’s a sign of a faulty camera
• The streetlight is broken
Answer: Droplets on the camera lens scatter the light
Tiny water droplets on the camera’s lens act as multiple small prisms/lenses. They refract and scatter the point source of light from the streetlamp, creating the artistic starburst or halo effect.
Q27. Why do some people need to wear different glasses for driving and reading?
• Fashion
• Their eyesight changes during the day
• They may have presbyopia, needing help for near vision, but their distance vision is also imperfect
• It’s a legal requirement
Answer: They may have presbyopia, needing help for near vision, but their distance vision is also imperfect
A common solution is bifocals or progressive lenses. The top part corrects for distance vision (e.g., slight myopia or astigmatism for driving), and the bottom part adds power for reading.
Q28. Why does a spoon handle look broken at the water’s surface in a glass?
• The water dissolves the spoon
• Due to refraction at the air-water boundary
• The spoon is made of a special material
• Due to reflection from the glass
Answer: Due to refraction at the air-water boundary
Light from the submerged part of the spoon bends away from the normal as it moves from water (denser) to air (rarer). This makes the spoon appear to be displaced, creating a “broken” look.
Q29. Why is it dangerous to look directly at the sun, especially during a partial solar eclipse?
• The sun is too bright
• The intense focused light can burn a spot on the retina without you feeling pain
• It can cause headaches
• It can damage the cornea
Answer: The intense focused light can burn a spot on the retina without you feeling pain
The eye’s lens focuses the sun’s powerful rays onto a tiny spot on the retina. This can cause solar retinopathy—a permanent burn scar on the light-sensitive cells. During an eclipse, the dimmer light tricks pupils into dilating, making the damage worse.
Q30. A person sees “floaters” – tiny specks drifting in their field of vision. What are these usually?
• Bugs in the air
• Dead cells or protein clumps in the vitreous humour
• Signs of a serious eye infection
• Dust on the cornea
Answer: Dead cells or protein clumps in the vitreous humour
The vitreous humour is a gel. Over time, tiny shreds of protein or cells can clump together, casting shadows on the retina. These are perceived as floaters and are usually harmless, though a sudden increase warrants a doctor’s visit.
Q31. Why are rear-view mirrors in cars often have a “day/night” flipping lever?
• To change the mirror’s colour
• To switch between a plane mirror and a convex mirror
• To switch between a plane mirror and a concave mirror
• To clean the mirror
Answer: To switch between a plane mirror and a convex mirror
In the “day” position, it acts as a normal plane mirror. At “night,” the lever tilts the mirror so you see a dimmer reflection from the front silvered surface, while the main glass surface, which is slightly convex, gives a wider but dimmer field of view, reducing headlight glare from behind.
Q32. A mirage of a pool of water on a hot road is caused by:
• Reflection from the road
• Refraction of light due to hot, less dense air near the ground
• Actual water evaporating
• Scattering of light
Answer: Refraction of light due to hot, less dense air near the ground
Air just above a hot road is hotter and less dense than cooler air above it. Light from the sky bends (refracts) as it passes through these layers. When it bends upwards into your eye, your brain interprets it as light coming from the ground, creating the illusion of a reflective water surface.
Q33. Why are lighthouse beams often designed to rotate?
• To save electricity
• To create a flashing pattern that is easily identifiable
• To look pretty
• To scan for ships
Answer: To create a flashing pattern that is easily identifiable
A rotating beam creates a unique sequence of flashes (e.g., one flash every 10 seconds). Sailors can identify which lighthouse they are seeing based on this “light character,” helping with navigation and avoiding confusion with other lights.
Q34. Why do your eyes sometimes feel tired after trying to read in a moving vehicle?
• The vibration of the vehicle
• Your eyes are constantly trying to re-focus (accommodate) as the distance to the book changes minutely
• The change in air pressure
• The print is too small
Answer: Your eyes are constantly trying to re-focus (accommodate) as the distance to the book changes minutely
Even small vibrations and movements of the vehicle cause the book to jiggle slightly closer and farther from your eyes. Your ciliary muscles work overtime to constantly adjust focus, leading to muscle fatigue and eye strain.
Q35. Why does a white shirt look white under both sunlight and fluorescent light?
• It reflects all colours of light
• It absorbs all colours of light
• It only reflects white light
• It emits its own white light
Answer: It reflects all colours of light
A white object reflects (scatters) all the wavelengths of visible light that fall on it. Whether the light source is sunlight (full spectrum) or fluorescent light (different mix of colours), the shirt reflects whatever it receives, so we perceive it as white.
Q36. A person who has had cataract surgery (lens replacement) often needs reading glasses afterward. Why?
• The surgery damages the ciliary muscles
• The new artificial lens is usually set for clear distance vision
• The surgery causes presbyopia
• The retina is affected
Answer: The new artificial lens is usually set for clear distance vision
The artificial intraocular lens (IOL) implanted during cataract surgery has a fixed focal length, unlike the natural flexible lens. It is typically set to focus light from distant objects perfectly on the retina, but it cannot change shape for near vision, necessitating reading glasses.
Q37. Why do 3D movies require you to wear special glasses?
• To make the screen look brighter
• To separate two slightly different images for each eye
• To protect your eyes from the projector light
• To make the colours more vibrant
Answer: To separate two slightly different images for each eye
The movie projects two images from different angles (like our two eyes). The glasses (polarized or colour-filtered) ensure your left eye only sees the left-eye image and your right eye only sees the right-eye image. Your brain then fuses them to create the perception of depth.
Q38. Why does a peacock’s feather appear to change colour when viewed from different angles?
• Due to pigments that move
• Due to interference and scattering of light from microscopic structures
• Due to reflection from nearby objects
• Due to an optical illusion
Answer: Due to interference and scattering of light from microscopic structures
This is “structural colour.” The feather has tiny, precise structures that interfere with light waves. Depending on the viewing angle, different wavelengths (colours) are reinforced or cancelled, creating iridescence (shifting colours).
Q39. A pilot flying at high altitude sees a darker blue sky above and a lighter blue near the horizon. Why?
• The horizon is closer to the ground
• Near the horizon, you look through more atmosphere, which scatters more light (including more white light)
• The earth reflects blue light
• Clouds are only at the horizon
Answer: Near the horizon, you look through more atmosphere, which scatters more light (including more white light)
Looking straight up, you look through the least atmosphere, seeing the pure, dark blue from Rayleigh scattering. Looking towards the horizon, the path through the atmosphere is much longer. More scattering occurs, and some of that scattered light (from all colours) gets re-scattered towards you, adding white light and making the blue appear paler.
Q40. Why is it easier to read black text on a white background than white text on a black background for long periods?
• Personal preference
• Black text reflects less light, causing less glare and pupil constriction, reducing strain
• White text is harder to print
• Black backgrounds absorb the screen light
Answer: Black text reflects less light, causing less glare and pupil constriction, reducing strain
A bright white background reflects a lot of light, causing more glare and making your pupils constrict. The high contrast can be harsh. A dark background with bright text forces your pupils to dilate, and the bright text itself can cause a “halation” effect (light bleed), making fine details of the letters harder to distinguish, leading to faster fatigue.
Q41. A cook uses a glass lid to check on boiling pasta without lifting it. Why does the lid get foggy with droplets, making it hard to see?
• The steam condenses into tiny water droplets on the cooler glass
• The pasta releases oil
• The glass is melting
• It’s a sign the pasta is done
Answer: The steam condenses into tiny water droplets on the cooler glass
The hot, moist steam from the boiling water hits the relatively cooler surface of the glass lid. The water vapour condenses into countless tiny water droplets. These droplets scatter light in all directions (Tyndall Effect), turning the transparent glass into a translucent, foggy surface that obscures the view.
Q42. Why do some people see halos around streetlights at night, especially after certain eye surgeries or with cataracts?
• Their glasses are dirty
• Light is being scattered or diffracted within the eye
• It’s a sign of good night vision
• The streetlights have special bulbs
Answer: Light is being scattered or diffracted within the eye
Conditions like cataracts (cloudy lens) or corneal edema (swelling) create microscopic irregularities. Light from a point source (like a streetlamp) gets scattered as it passes through these imperfections, spreading out and forming a halo or starburst pattern on the retina.
Q43. A photographer uses a polarizing filter to take a picture of a landscape with a blue sky. What does it do?
• Makes the whole picture darker
• Reduces reflections from non-metallic surfaces and darkens the blue sky
• Makes all colours more vivid by adding light
• Blurs the background
Answer: Reduces reflections from non-metallic surfaces and darkens the blue sky
Sunlight scattered by air molecules becomes partially polarized. A polarizing filter can be rotated to block this polarized light, making the blue sky appear deeper and darker. It also blocks glare (polarized reflections) from water, leaves, and glass.
Q44. Why does a room look darker when you turn off a bright overhead light, even if there is still light from a window?
• Your pupils take time to dilate
• The window light is not enough
• Your eyes were adapted to the brighter light
• Both A and C
Answer: Both A and C
This is “dark adaptation.” Under the bright light, your pupils were small and your retina’s rods were less active. When the light is turned off, it takes several minutes for your pupils to dilate and for the rods (responsible for low-light vision) to become fully sensitive again.
Q45. A person with one functional eye can still judge distances fairly well by moving their head. How does this work?
• Hearing helps
• Motion parallax: closer objects appear to move faster than distant ones when you move your head
• The brain memorizes sizes
• They are just guessing
Answer: Motion parallax: closer objects appear to move faster than distant ones when you move your head
This is a monocular depth cue. When you move your head side-to-side, the images of nearby objects shift position on your retina more rapidly than those of distant objects. Your brain uses this relative motion to estimate distances.
Q46. Why are the letters on a hospital patient’s chart (Snellen chart) black on white?
• Tradition
• To maximize contrast for accurate vision testing
• Because ink is cheap
• To look medical
Answer: To maximize contrast for accurate vision testing
High contrast (black on white) ensures that the test measures the eye’s ability to resolve shapes (visual acuity) and not its ability to distinguish low-contrast objects. Any blurring or refractive error will immediately make the black letters merge with the white background, providing a clear test result.
Q47. A magician appears to “saw a person in half” using angled mirrors. What principle makes this illusion work?
• Refraction bends the light
• Mirrors reflect the image of the person’s lower body, making it appear detached
• The box is made of special material
• Audience hypnosis
Answer: Mirrors reflect the image of the person’s lower body, making it appear detached
The box contains strategically placed mirrors at 45-degree angles. These mirrors reflect the sides of the box or the person’s folded-up lower legs, creating the illusion that the lower half of the body is visible but separated, while the person is actually curled up.
Q48. Why do virtual reality (VR) headsets sometimes cause motion sickness or eye strain?
• The screens are too close to the eyes
• There can be a mismatch between what the eyes see (movement) and what the inner ear feels (no movement)
• The graphics are too realistic
• The headset is too heavy
Answer: There can be a mismatch between what the eyes see (movement) and what the inner ear feels (no movement)
This is “VR sickness.” Your eyes tell your brain you are moving through a virtual world, but your inner ear’s balance system reports that your body is stationary. This sensory conflict can cause nausea, dizziness, and eye strain as the brain tries to reconcile the information.
Q49. A person looks at their reflection in the curved side of a shiny spoon. Their reflection is upside down. Which side of the spoon are they looking into?
• The convex (outer, bulging) side
• The concave (inner, hollow) side
• It works on both sides
• The handle of the spoon
Answer: The concave (inner, hollow) side
The concave side of a spoon acts like a concave mirror. When your face is placed beyond its focal point, it forms a real, inverted (upside-down) image. The convex side always creates a smaller, upright virtual image.
Q50. A barber places a large mirror on the wall in front of you and a smaller mirror behind you, allowing you to see the back of your head. How does this work?
• The large mirror is magic
• The small mirror reflects the back of your head into the large mirror, which then reflects it to your eyes
• Light goes around corners
• The mirrors are connected electronically
Answer: The small mirror reflects the back of your head into the large mirror, which then reflects it to your eyes
Light from the back of your head travels to the small mirror held behind you. That mirror reflects the light towards the large wall mirror in front of you. Finally, the wall mirror reflects that light into your eyes, allowing you to see the reflection of the back of your head.