The spreading of light by the air molecules is called scattering of light. The colour of the scattered light depends on the size of particles. The amount of scattering of light depends on the wavelength of light. When light from sun enters the earth’s atmosphere, it gets scattered by the dust particles and air molecules present in the atmosphere. The path of sunlight entering in the dark room through a fine hole is seen because of scattering of the sun light by the dust particles present in its path inside the room.
49. To an astronaut in spaceship the Earth appears: [A] blue [B] red [C] dark [D] white
50. The colour of sky appears blue, it is due to the: [A] refraction of light through the atmosphere [B] dispersion of light by air molecules [C] scattering of light by air molecules [D] all of these. 51. Due to atmospheric refraction, the apparent length of a day: [A] increases by 4 minutes [B] increases by 2 minutes [C] decreases by 2 minutes [D] remains the same
52. Twinkling of stars and non-twinkling of planets is accounted for by: [A] atmospheric refraction [B] atmospheric scattering [C] total internal reflection [D] dispersion of light
Answers
Answer:
49. (A) Blue
50. [C] scattering of light by air molecules
51. [A] increases by 4 minutes
52. [A] atmospheric refraction
Explanation:
49. The blue color of sunlight is scattered the most by atmosphere in its
surrounding. So when seen from space the blue colour is reflected to astronaut's eyes and hence it appears blue.
50. The blue coloured light has shorter wavelength than dust particles present in atmosphere , and hence gets scattered all around the sky.
51. Due to atmospheric refraction sun rises 2 minute before actual sun rise, and sets 2 minute after actual sunset.
The time from sunrise to sunset increased by:2+2=4.
52. Due to the varying optical densities of air at various altitude the atmosphere refracts light coming from stars by different amount in short time interval (from one moment to next. )