RAINBOW ACADEMY SR. SEC. SCHOOL
TEENPANI BAREILLY ROAD,
HALDWANI
CLASS X
Subject – Science
Date - 10 December,2020
Question1. A star appears slightly higher (above) than its actual position in the sky.
Answer. The gradual change in the refractive index of different layers of the atmosphere due to the varying conditions of it causes atmospheric refraction. When starlight enters the atmosphere, it gets refracted continuously. The higher level of air acts as a rarer medium while the dense air near the surface of earth acts as a denser medium. So, the atmosphere bends the starlight towards the normal. As a result, the apparent position of star is slightly different from its actual position. Thus, star appears slightly higher (above) than its actual position in the sky.Question2. What is the colour of the clear sky during day time? Give reason for it. [All India]
Answer. Clear sky appears blue.
Reason: When sunlight passes through the atmosphere having the molecules of air and other fine particles, whose size is smaller than the wavelength of visible light, these molecules and particles scatter the blue colour more strongly than the other colours of spectrum as the wavelength of blue colour is more. This scattered blue light enters our eye. So, the colour of sky appears blue to us during day time.
Answer. Clear sky appears blue.
Reason: When sunlight passes through the atmosphere having the molecules of air and other fine particles, whose size is smaller than the wavelength of visible light, these molecules and particles scatter the blue colour more strongly than the other colours of spectrum as the wavelength of blue colour is more. This scattered blue light enters our eye. So, the colour of sky appears blue to us during day time.
Question3. Why are stop signals on roads in red coloured light ?
Answer. When light falls on the signal, all colours are scattered much more than that of red colour. So the red colour suffering least scattering remains confined around the signal, which in turn illuminates the signal significantly. Thus, the danger signals can be seen from very far off distances. Moreover, among all colours, red colour or red light is scattered least by smoke or fog. Hence, red signals are visible even through the smoke or fog.
Question4. What would have been the colour of sky if the earth had no atmosphere ? Give reason for your answer.
Answer. If the earth had no atmosphere, the colour of the sky would have been dark. The colour of sky depends on the scattering the sunlight due to the atmosphere. No atmosphere means no scattering of light.
Answer. If the earth had no atmosphere, the colour of the sky would have been dark. The colour of sky depends on the scattering the sunlight due to the atmosphere. No atmosphere means no scattering of light.
