41. The sun appears oval shaped or flattened due to
42. The velocity of waves of all colours is same in:
43. To an astronaut in a spaceship, the colour of earth appears
44. Twinkling of stars and non-twinkling of planets is accounted for by
45. Twinkling of stars is due to atmospheric
46. Tyndall effect is due to
47. What is the colour of the sky when it is seen from moon's surface?
48. What is the time difference between actual sunset and apparent sunset?
49. What will be the colour of sky if there is no atmosphere on the earth?
50. When a ray of light travels from an optically denser medium to an optically rarer medium
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