WORKSHEET – CHAPTER 10: THE HUMAN EYE AND THE COLOURFUL WORLD

SECTION A – MULTIPLE CHOICE QUESTIONS (20 MCQs)

  1. The part of the human eye that controls the size of the pupil is:
     a) Cornea
     b) Iris
     c) Retina
     d) Lens

  2. The near point of a normal human eye is:
     a) 0 cm
     b) 25 cm
     c) 50 cm
     d) Infinity

  3. A myopic person has:
     a) Elongated eyeball
     b) Shortened eyeball
     c) No eyeball change
     d) Weak retina

  4. Myopia is corrected by:
     a) Convex lens
     b) Concave lens
     c) Cylindrical lens
     d) Bifocal lens

  5. Presbyopia occurs due to:
     a) Weakening of ciliary muscles
     b) Elongated eyeball
     c) Thick lens
     d) Long retina

  6. The focal length of eye lens is controlled by:
     a) Cornea
     b) Retina
     c) Iris
     d) Ciliary muscles

  7. The splitting of white light into seven colours is called:
     a) Scattering
     b) Dispersion
     c) Reflection
     d) Refraction

  8. Which colour deviates the most in a prism?
     a) Red
     b) Orange
     c) Green
     d) Violet

  9. Twinkling of stars is due to:
     a) Dispersion
     b) Atmospheric refraction
     c) Reflection
     d) Scattering

  10. The sky appears blue because:
     a) Dispersion
     b) Scattering
     c) Refraction
     d) TIR

  11. Red light is used in traffic signals because it:
     a) Has highest frequency
     b) Is scattered least
     c) Is dispersed more
     d) Appears beautiful

  12. Cataract affects which part of the eye?
     a) Retina
     b) Lens
     c) Iris
     d) Cornea

Numerical MCQs
  1. A myopic eye forms image 50 cm in front of retina. Power of lens needed?
     (Focal length = –50 cm)
     a) –2 D
     b) –1 D
     c) +2 D
     d) +1 D

  2. A hypermetropic eye has near point at 50 cm. Lens power required to set near point at 25 cm is approx:
     a) +2 D
     b) +1 D
     c) –4 D
     d) –1 D

  3. Power of a convex lens with focal length 40 cm is:
     a) +2.5 D
     b) +4 D
     c) +1.5 D
     d) +0.25 D

Case-Based MCQs

Read the case and answer Q16–20:

A student uses a prism to obtain a spectrum of white light. He observes that violet bends most and red bends least.

  1. The phenomenon responsible is:
     a) Refraction
     b) Reflection
     c) Dispersion
     d) Diffraction

  2. The difference in deviation between violet and red is called:
     a) Angular shift
     b) Angular dispersion
     c) Scattering angle
     d) Frequency gap

  3. Red light deviates least because it has:
     a) Highest wavelength
     b) Lowest wavelength
     c) Highest frequency
     d) Lowest speed

  4. The sequence of colours is:
     a) VIBGYOR
     b) RYBGVIO
     c) VIGYBOR
     d) RGBYVOI

  5. If prism angle increases, dispersion:
     a) Decreases
     b) Increases
     c) Remains same
     d) Becomes zero

SECTION B – ASSERTION & REASON (10 Questions)

  1. A: Myopia is corrected using concave lens.
     R: Concave lens diverges light rays.

  2. A: Hypermetropia is corrected using convex lens.
     R: Convex lens converges light rays.

  3. A: The sky looks blue.
     R: Blue light scatters the least.

  4. A: Stars appear to twinkle.
     R: Density of air layers in atmosphere keeps changing.

  5. A: Rainbow is formed by water droplets.
     R: Water droplets act as tiny prisms.

  6. A: Red light is used in fog lamps.
     R: Red light is scattered least due to long wavelength.

  7. A: A prism causes deviation and dispersion.
     R: Refractive index of material is same for all colours.

  8. A: Dusty air appears yellowish.
     R: Larger particles scatter light of longer wavelength.

  9. A: Cataract causes blurred vision.
     R: The cornea becomes opaque during cataract.

  10. A: Near point of human eye is 25 cm.
     R: This distance gives maximum accommodation.

SECTION C – ONE-WORD / VERY SHORT ANSWERS (10)

  1. Define accommodation of eye.
  2. What is far point of a normal eye?
  3. Write the SI unit of power of lens.
  4. Name the defect caused by aging.
  5. Define dispersion.
  6. Give one use of concave lens.
  7. Name the part of eye where image is formed.
  8. What causes twinkling of stars?
  9. Which colour scatters most?
  10. What is angular dispersion?

SECTION D – SHORT ANSWER QUESTIONS (8)

  1. Why do stars twinkle but planets do not?
  2. What is presbyopia? How can it be corrected?
  3. Explain formation of rainbow in the sky.
  4. A lens has power +3 D. Calculate focal length.
  5. Why is sky blue during day but reddish during sunrise and sunset?
  6. Draw a ray diagram showing dispersion through prism.
  7. State the laws of refraction.
  8. Why is red light used in traffic signals?

SECTION E – LONG ANSWER QUESTIONS (5)

Q1. (Numerical + Theory – 5 Marks)

A boy cannot see distant objects clearly. His far point is 1.5 m.

(a) Identify the defect.
 (b) Draw ray diagram showing defect.
 (c) Calculate power of corrective lens.
 (d) Draw ray diagram showing correction.
 (e) Write two causes of this defect.

Q2. (Case-Based – Rainbow Formation)

A student observes a rainbow after rainfall.

(a) Explain conditions necessary for rainbow formation.
 (b) Explain the sequence of colours using dispersion.
 (c) Draw a labelled diagram showing all steps inside water droplet.
 (d) Why is rainbow seen only when the Sun is behind observer?

Q3. (HOTS – Scattering & Colour of Sky)

(a) Explain Rayleigh scattering.
 (b) Why is the sky blue?
 (c) Why is the Sun red during sunrise/sunset?
 (d) Why does the sky appear dark to astronauts in space?

Q4. (Prism Refraction – 5 Marks)

A beam of white light passes through a triangular prism.

(a) Draw diagram showing refraction and dispersion.
 (b) Define angle of deviation.
 (c) Define mean deviation and angular dispersion.
 (d) Why does violet deviate more than red?
 (e) What happens when white light is replaced with red light?

Q5. (Eye Structure & Function – 5 Marks)

(a) Draw a neat labelled diagram of the human eye.
 (b) Explain the function of: cornea, iris, retina, ciliary muscles.
 (c) What is accommodation?numericals
 (d) Why is image inverted on retina but we see upright?
 (e) How does the brain process visual information?

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