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Question
(a) Explain the following-
(i) Atmospheric refraction and advance sunrise.
(ii) Tyndall effect.
(iii) Draw the ray diagram of an eye suffering from short sightedness.
(i) Atmospheric refraction and advance sunrise.
(ii) Tyndall effect.
(iii) Draw the ray diagram of an eye suffering from short sightedness.
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Solution
(i) Atmospheric refraction is the deviation of light or other electromagnetic wave from a straight line as it passes through the atmosphere due to the variation in air density as a function of height.
Advance Sunrise:The sunrise is advanced due to atmospheric refraction of sunlight. An observer on the earth sees the sun two minutes before the sun reaches the horizon. A ray of sunlight entering the earth's atmosphere follows a curved path due to atmospheric refraction before reaching the earth. This happens due to a gradual variation in the refractive index of the atmosphere. For the observer on the earth, the apparent position of the sun is slightly higher than the actual position. Hence, the sun is seen before the sun reaches the horizon.
(ii) The scattering of a beam of light by the particles of a colloid is called tyndall effect. When we apply torch light on a glass of milk, then the path of the light becomes visible; but it is not so in the case of water because in milk, light is scattered by its very fine particles. Tyndall effect can be observed when sunlight passes through the canopy of a dense forest. In forest, mist contains tiny droplets of water, which act as particles of colloid dispersed in air.
(iii) The ray diagram of an eye suffering from short sightedness in shown.
Advance Sunrise:
The sunrise is advanced due to atmospheric refraction of sunlight. An observer on the earth sees the sun two minutes before the sun reaches the horizon. A ray of sunlight entering the earth's atmosphere follows a curved path due to atmospheric refraction before reaching the earth. This happens due to a gradual variation in the refractive index of the atmosphere. For the observer on the earth, the apparent position of the sun is slightly higher than the actual position. Hence, the sun is seen before the sun reaches the horizon.
(ii) The scattering of a beam of light by the particles of a colloid is called tyndall effect. When we apply torch light on a glass of milk, then the path of the light becomes visible; but it is not so in the case of water because in milk, light is scattered by its very fine particles. Tyndall effect can be observed when sunlight passes through the canopy of a dense forest. In forest, mist contains tiny droplets of water, which act as particles of colloid dispersed in air.
(iii) The ray diagram of an eye suffering from short sightedness in shown.
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