10 Question-Answer on Doppler Effect in light
1. A star is emitting yellow light. If it is accelerated towards earth, then to an observer on earth, it will appear
(a) Shining yellow
(b) Gradually changing to violet
(c) Gradually changing to red
(d) Unchanged
Ans: (b)
2. When a source of light is receding away from an observer, then the spectral lines will get displaced towards
(a) Violet region
(b) Red region
(c) Ultraviolet region
(d) Blue region
Ans: (b)
3. Radio waves are sent from radar towards an aero plane and these waves again reach the radar after reflection from aero plane. If the aero plane is moving towards radar, then the wavelength of reflected wave:
(a) Increased
(b) Decreased
(c) Does not change
(d) May have any value.
Ans: (b)
4. An observer on earth observes that wavelength of spectral line in spectrum of a Milky Way shifts towards red end of spectrum. According to observer, the milky way is:
(a) Approaching the earth
(b) Receding away from earth
(c) Stationary
(d) Rotating about its own axis.
Ans: (b)
5. For which of the following waves, the Doppler effect is not applicable?
(a) Shock waves
(b) Ultrasonic waves
(c) Sonic waves
(d) Electromagnetic waves.
Ans: (a)
6. Which of the following is not the use of Doppler effect?
(a) Discovery of twin stars
(b) To determine the velocity of milky way
(c) To determine the radius of earth
(d) To determine the velocity of submarine.
Ans: (c)
7. When the light of source is moving towards an observer,
(a) Wavelength of light decreases
(b) Wavelength of light increases
(c) Wavelength of light remains unchanged
(d) Velocity of light increases
Ans: (a)
8. In the context of Doppler effect in light, the term red shift signifies
(a) Decreases in frequency
(b) Increases in frequency
(c) Decreases in intensity
(d) Increases in intensity
Ans: (a)
9. The sun is rotating about its own axis. The spectral lines emitted from the two ends of its equator, for an observer on the earth will show
(a) Shift towards red end
(b) Shift towards violet end
(c) No shift
(d) Shift towards red from one end and shift towards violet from other end.
Ans: ( d)
10. A star emits light of 5500 A wavelengths. It appears blue to an observer on earth. It means
(a) Star is moving away from earth
(b) Star is stationary
(c) Star is moving towards earth
(d) None of above.
Ans: (c)