Question

Q9. Why stars appear to twinkle at night?

a) because the star changes its position relative to earth

b) because the distance of star varies when earth rotates

c) because the light of stars travels in different medium

d) because the atmosphere reflects the light at different angles

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Answer 1

Q9. Why stars appear to twinkle at night?

Answer- d) because the atmosphere reflects the light at different angles

Answer 2

The correct solution is option d, the atmosphere reflects the light at different angles.

• The twinkling of star is due to the atmospheric refraction of light.
• Atmospheric refraction is the bending of light on passing through the earth's atmosphere. It occurs in a medium of gradually changing refractive index.
• The apparent position of the star is slightly different from its actual position because of the atmospheric bending of starlight towards the normal.
• The stars are very distant and appear as point-sized sources of light.
• The apparent position of the star fluctuates as the path of rays of starlight goes on varying slightly due to which the amount of starlight entering the eyes flickers and sometimes appear brighter or fainter. This phenomenon is called the twinkling effect.