Human Eye and Colourful World Science - Human Eye and Colourful World

• A
  Dispersion of light by water droplets.
• ✓
  Refraction of light by different layers of varying refractive indices.
• C
  Scattering of light by dust particles.
• D
  Internal reflection of light by clouds.

Answer: B.

• A
  Is scattered the most by smoke or fog.
• ✓
  Is scattered the least by smoke or fog.
• C
  Is absorbed the most by smoke or fog.
• D
  Moves fastest in air.

Answer: B.

• A
  +0.5D
• ✓
  -0.5D
• C
  +0.2D
• D
  -0.2D

Answer: B.

• A
  Reflection, refraction and dispersion.
• B
  Refraction, dispersion and total internal reflection.
• ✓
  Refraction, dispersion and internal reflection.
• D
  Dispersion, scattering and total internal reflection.

Answer: C.

• ✓
  Are relaxed and lens becomes thinner.
• B
  Contract and lens becomes thicker.
• C
  Are relaxed and lens becomes thicker.
• D
  Contract and lens becomes thinner.

Answer: A.

• ✓
  1. She is suffering from myopia.
  2. $\text{f}=\frac{1}{\text{P}}=-\frac{1}{4.5}=-0.22\text{m}=-22\text{cm}.$
  3. Concave lens.

Answer: A.

• ✓
  No. Light emitted by distant stars (act as point sources of light) passes through the atmosphere of the earth before reaching our eyes. The atmosphere of the earth is not uniform but consists of many layers of different densities. The layers close to the surface of the earth are optically denser. As we go higher and higher, the density of layers and refractive index decreases progressively. As the light from a star enters the upper­most layer of the atmosphere, it bends towards the normal as it enters the next layer. This process continues till the light enters our eyes. So due to refraction of light, the apparent position of the star is different from the actual position of the star (Figure).
  

Answer: A.

• ✓
  
  

Answer: A.

• ✓
  For this, one prism is placed near another prism so that one prism is in erect position and another prism is in inverted position. When ray of white light enters the first prism, dispersion of light takes place. When lights of different colours pass through the second prism, they recombine to make a ray of white light.

Answer: A.

• ✓
  Human eyes have power of accommodation. When we have to see distant objects, the eye muscles relax and lens becomes thin. Due to this, the focal length of the lens increases and the eye is able to see distant objects. When we have to see nearby objects, the eye muscles contract and lens becomes thick. Due to this, the focal length of the lens decreases and the eye is able to see nearby objects.

Answer: A.