Class 10 Science Chapter 10 MCQ

Here, all the statements are correct. Hence, your answer will be option [D].

At noon the sun appears white because the light from the sun is directly overhead and travel relatively shorter distance. The sun appears white as only a little of the blue and violet colours are scattered.

The sky appears blue because some of the blue component of sunlight is scattered by the gas molecules (nitrogen and oxygen) present in the air.

Here, all the statements are correct. Hence, your answer will be option [D].

Rainbow is caused by dispersion, refraction and internal reflection of sunlight by tiny water droplets, present in the atmosphere and always formed in a direction opposite to that of the sun. The water droplets act like a small prism. They refract and disperse the incident sunlight, then reflect it internally and finally refract it again when it comes out of the raindrop.

The twinkling of star is due to atmospheric refraction of light of stars. These lights, on entering the earth’s atmosphere, undergoes refraction continuously before it reaches the earth. The path of rays of light coming from the distant star goes on varying slightly, the apparent position of the star fluctuates and the amount of starlight entering the eye flickers. The star sometimes appears brighter and at some other time, fainter gives us the twinkling effect.

When the eye is looking at a distant object, the eye is said to be unaccommodated because it is the relaxed state of the eye.

The clear sky appears blue is due to Rayleigh scattering of sunlight. The molecules in the air scatter blue light from the sun more than they scatter red light.

As the person has the eye defect, myopia, therefore, a concave lens has to be used whose focal length will be, f = – 2 m (using sign convention). Thus, Power, P = 1/f (where, f is focal length in metre) = 1/- 2 = -0.5 D

As the light from a far-off star comes towards the earth, it bends towards the normal because the air is denser closer to the surface of the earth.

Here, all the statements are correct. Hence, your answer will be option [D].

Stars twinkle because they are far away. The planets do not twinkle at night because they are nearer to the earth.

Here, all the statements are correct. Hence, your answer will be option [D].

The danger signals installed at the top of tall buildings are red in colour because among all other colours, red colour is scattered the least by smoke of fog. This is primarily because wavelength of red colour is the largest. Thus, it can be easily seen from a distance.

The bluish color of water in deep sea is due to scattering of light as the very fine particles in water scatter mainly blue light. The red, green, orange and yellow having longer wavelengths are absorbed more strongly by water then blue which has shorter wavelength. So, when white light from the sun enters the sea, it is mostly the blue that gets returned.

The reddish appearance of the sun at sunrise or sunset is due to least scattering of red light. The red light has the maximum wavelength. The rays of light have to travel a larger part of the atmosphere.

Actually, in refraction through a glass prism the emergent ray is deviated from its original direction by a certain angle. And we say that light rays get deviated on passing through a glass prism. Therefore, in refraction through a glass prism, the emergent ray is not parallel to the incident ray. Q.29. When light rays enter the eye, most of the refraction occurs at the

When the light rays enters the eye through a thin membrane, forms the transparent bulge on the front surface of the eyeball, called the cornea. Most of the refraction for the light rays entering the eye occurs at this outer surface of the cornea.

If a man driving a car can see a distant road sign distinctly but cannot read the odometer on the dashboard of the car clearly, it suggests that the near point of his eyes has receded.

A person with myopia can see nearby objects clearly. While a person with hypermetropia can see distant objects clearly.

The nitrogen and oxygen gas molecules present in the atmosphere are smaller than the wavelength range of visible light. So, when light coming from the sun hits this very small air molecules, it behaves differently. Since, the different colours of white light have different wavelengths, so they are affected differently. The lower wavelengths lights (blues) are scattered much more by the air molecules but the higher wavelengths lights (reds) are scattered much less.

The thickness of the eye lens is increased to focus the image of a nearby object on the retina of the eye.

The human eye possesses the power of accommodation to focus on objects at different distances.

As the far point of the eye is closer to him than normal, he can see nearby objects, but not distant objects, clearly.

Having two eyes gives a person a wider field of view.