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NMMS – Physics – Light


Main points

  • Light is an important form of energy in the universe, which creates in us the sensation of vision.
  • Speed of light is different in different media. The speed of light in vacuum is maximum.
  • Mirrors are surfaces which reflect light well.
  • Bouncing back of light from a surface is called reflection.
  • While looking at the image in a mirror, we see that the left side of the object is seen as the right side of the image and the right side is seen as the left side. The property is called lateral inversion.
  • When the size of the angle between two plane mirrors decreases, the number of images increases.
  • Refraction of light is the change in the direction of the movement of light when it passes from one transparent medium into another of different density.


Laws of refraction

  • i) The incident ray, the refracted ray and the normal at the point of incidence all lie in the same plane.

ii)sin i/sin r, a constant. This constant is called the refractive index of the medium.

  • When light enters from one transparent medium to another transparent medium the velocity of light changes. This is the reason for refraction.
  • The rays of light while going from rarer medium to denser medium will bend towards the normal.


1)   ……… light is the change in the direction of the movement of light, when it passes from one transparent medium into another.

  1. Refraction b. Reflection
  2. Dispersion d. Scattering              Ans: (a)


2)   Which of the following is the reason for the refraction of light?

  1. Difference in density             b. Angle of incidence
  2. Angle of refraction d. Critical angle       Ans: (a)


3)   Refractive index of a medium depends upon ………..?

  1. Density of the medium b. Wavelength of light
  2. Angle of incidence and reflection d. All of the above.  Ans: (d)


4)   From the following which one has more density of light?

  1. Water b. Air         c. Diamond         d. Glass           Ans: (c)


5)   When a ray of light passes from one medium to another, then which property of light will not change?

  1. Speed b. Frequency
  2. Wave length d. Intensity          Ans: (b)


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