CLASS - 10 SCIENCE IMPORTANT QUESTIONS OF MARK 3 FOR BOARD EXAMINATION
QUESTION NO. 45
What is the cause of dispersion of white light through glass prism ? Draw a ray diagram to show the path of light when two indentital glass prism are arranged together in inverted position with respect to each other and a narrow beam of white light is allowed to fall obliquely on one of the faces of the prism.
The splitting of light into its component colour is called dispersion.
When light passes through a prism, the different frequencies of light travel at different velocities. Because of refraction, the different velocities make the angle of refraction different, causing the light to travel in slightly different direction.
Write the function of the following in human eye.
(i) Cornea
(ii) Retina
(iii) Iris
Light enters the eye through a thin membrane called cornea.
What is atmospheric refraction ? Explain why the position of a star as seen by us is not its true position.
When the light rays pass through the atmosphere having layers of different densities and refractices then refraction of light takes place. This refraction of light by the earth's atmosphere is called atmospheric refraction.
The starlight, on entering the earth's atmosphere, undergoes refraction continuously before it reaches the earth. The atmospheric refraction occurs in a medium of gradually changing refractive index. Since the atmosphere bends starlight towards the normal, the apparent position of the star is slightly different from it actual position. The star appears slightly higher than it's actual position when viewed near the horizon.
State the difference in colours of the sun observed during sunrise/ sunset and noon. Give explanition of each.
Sun appears red at sunrise and sunset. At sunrise and sunset, sun is closer to the horizon. The sunlight passes through denser layer of air and covers longer distance before reaching our eyes. Most of the blue light gets scattered. The light that reaches to us is red.
That's why the sun appears red at sunrise.
At noon, the sun is overhead. The sunlight passes through rares layers of air and covers shorter distance before reaching our eye. So, at all colours of light are scattered equally. Hence the sun appears white.
Write the various eye defect in human and write how it can be corrected.
Myopia is also known as near - sightedness. A person with myopia can see nearby objects clearly, but cannot see distance object clearly.
This defect can be corrected by using a concave lens of suitable power.
Hypermetropia is also known as far - sightedness. A person with hypermetropia can see distance object clearly but cannot see nearby object clearly.
This defect can be corrected by using convex lens of appropriate power.
The power of accommodation of the eye usually decrease with ageing. They find it difficult to see nearby objects comfortably and distance object without corrective eye glasses.
Such people often requires bi - focal lenses.
ANSWER NO. 45
DISPERSION
The splitting of light into its component colour is called dispersion.
CAUSES OF DISPERSION OF LIGHT
When light passes through a prism, the different frequencies of light travel at different velocities. Because of refraction, the different velocities make the angle of refraction different, causing the light to travel in slightly different direction.
QUESTION NO. 46
Write the function of the following in human eye.
(i) Cornea
(ii) Retina
(iii) Iris
ANSWER NO. 46
(i) CORNEA
Light enters the eye through a thin membrane called cornea.
(ii) RETINA
It is the light sensitive part of the eye on which image is formed by the lens and send impulses to the brain via optive nerve.(iii) IRIS
Iris is a dark muscular diaphragm that controls the size of the pupil.QUESTION NO. 47
What is atmospheric refraction ? Explain why the position of a star as seen by us is not its true position.
ANSWER NO. 47
When the light rays pass through the atmosphere having layers of different densities and refractices then refraction of light takes place. This refraction of light by the earth's atmosphere is called atmospheric refraction.
The starlight, on entering the earth's atmosphere, undergoes refraction continuously before it reaches the earth. The atmospheric refraction occurs in a medium of gradually changing refractive index. Since the atmosphere bends starlight towards the normal, the apparent position of the star is slightly different from it actual position. The star appears slightly higher than it's actual position when viewed near the horizon.
QUESTION NO. 48
State the difference in colours of the sun observed during sunrise/ sunset and noon. Give explanition of each.
ANSWER NO. 48
Sun appears red at sunrise and sunset. At sunrise and sunset, sun is closer to the horizon. The sunlight passes through denser layer of air and covers longer distance before reaching our eyes. Most of the blue light gets scattered. The light that reaches to us is red.
That's why the sun appears red at sunrise.
At noon, the sun is overhead. The sunlight passes through rares layers of air and covers shorter distance before reaching our eye. So, at all colours of light are scattered equally. Hence the sun appears white.
QUESTION NO. 49
Write the various eye defect in human and write how it can be corrected.
ANSWER NO. 49
1. MYOPIA
Myopia is also known as near - sightedness. A person with myopia can see nearby objects clearly, but cannot see distance object clearly.
This defect can be corrected by using a concave lens of suitable power.
2. HYPERMETROPIA
Hypermetropia is also known as far - sightedness. A person with hypermetropia can see distance object clearly but cannot see nearby object clearly.
This defect can be corrected by using convex lens of appropriate power.
3. PRESBYOPIA
The power of accommodation of the eye usually decrease with ageing. They find it difficult to see nearby objects comfortably and distance object without corrective eye glasses.
Such people often requires bi - focal lenses.
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