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Question : 25
Total: 39
(A) Observe the following diagram and answer questions following it:
(B) The colour of clear sky from the earth appears blue but from the space it appears black. Why?
OR
(B) The colour of clear sky from the earth appears blue but from the space it appears black. Why?
Solution:
(A) (i) Myopia.
(ii) Prolonged reading and other activities of close-up with eyes; genetic causes; environmental stress; etc.
(iii) Concave lens is diverging lens, it diverges the coming rays to meet them on retina.
OR
(B) The molecules of air and other fine particles in the atmosphere have size smaller than the wavelength of visible light. These are more effective in scattering light of shorter wavelengths at the blue end than light of longer wavelengths at the red end. The red light has a wavelength about 1.8 times greater than blue light. Thus, when sunlight passes through the atmosphere, the fine particles in air scatter the blue colour (shorter wavelengths) more strongly than red. The scattered blue light enters our eyes. In space with no atmosphere, there is no scattering. Therefore, the sky looks black.
(ii) Prolonged reading and other activities of close-up with eyes; genetic causes; environmental stress; etc.
(iii) Concave lens is diverging lens, it diverges the coming rays to meet them on retina.
OR
(B) The molecules of air and other fine particles in the atmosphere have size smaller than the wavelength of visible light. These are more effective in scattering light of shorter wavelengths at the blue end than light of longer wavelengths at the red end. The red light has a wavelength about 1.8 times greater than blue light. Thus, when sunlight passes through the atmosphere, the fine particles in air scatter the blue colour (shorter wavelengths) more strongly than red. The scattered blue light enters our eyes. In space with no atmosphere, there is no scattering. Therefore, the sky looks black.
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