Class 10 Science Chapter 10 MCQ

Iris is a flat, colored, ring shaped membrane behind the cornea of the eye. There is a hole in the middle of the Iris which is called pupil of the eye. Therefore, pupil is a hole in the middle of the Iris.

The sun appears red at sunset because, at that time, the sun is near the horizon and, therefore, sunlight has to travel through a greater thickness of the earth’s atmosphere.

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.

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 sun appears red at sunset not because of the atmospheric refraction of light but because of the scattering effect of light.

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.

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.

the whole purpose of using a concave lens here is to reduce the converging power of the eye-lens. The concave lens used here decreases the converging power of the eye-lens and helps in forming the image of distant object on the retina of the myopic eye.

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

The whole purpose of using a convex lens is to increase the converging power of the eye-lens. The convex lens used in spectacles increase the converging power of islands and helps in forming the image of a nearby object on the retina of the eye.

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.

Predators have both the eyes at the front of their heads so that they can judge the distance of their prey accurately.

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.

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.

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

The focal length of the eye lens increases when eye muscles relaxed and becomes thinner. The sharp image of the distant object is formed at the retina. This enables us to focus accurately on distant objects.

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 term ‘accommodation’ as applied to the eye refers to its ability to vary the focal length of the lens.

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.