Class 8 Science Chapter 13 MCQ

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

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

The image formed by a plane mirror is virtual or unreal and it is also created behind the mirror. The image formed in a plane mirror is the same distance behind the mirror and the same size as the object as the object in front of it. And the image formed by a plane mirror is erect and always laterally inverted.

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

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

The farthest point on the eye at which an object can be seen clearly is known as the “far point” of the eye. The nearest point up to which the eye can see an object clearly without any strain, is called the near point of the eye. The near point of a normal human eye is at a distance of 25 cm from the eye. This means, the most comfortable distance at which one can read a book with normal eyes is about 25 cm from the eyes.

Cones are sensitive to bright light and they sense color. However, rods are sensitive dim light.

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

We know that a plane mirror forms only a single image of an object placed in front of it. When two plane mirrors are kept inclined at an angle, they can form multiple images of an object. This is because the image of an object formed in one plane mirror acts as a object for the other plane mirror. Number of images formed = 360 degree / x – 1

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

The objects which do not emit their own light are called “non luminous” objects. Actually, the moon the non-luminous objects cannot make their own light. The moon, earth, table, chair, book, trees, plants, flowers, human beings, mirror, diamond are some of the examples of non-luminous objects.

A periscope works on the reflection of light from two plane mirrors arranged parallel to one another. It is an optical device. The principal followed in this device is reflection of light between two mirrors which are parallel to each other. Light from object incidence on the mirror and reflected to the mirror which is parallel to earlier mirror. The reflection from the latter mirror is reflected to eyes. This device is used to view the objects which are not in eyesight level. This device is majorly used in submarines and in army bunker.

The deficiency of one of the following in the diet of a person for a considerable time can lead to a disease called night blindness. This one is “Vitamin A”. The impaired dark adaptation of eyes is called as night blindness. People with this impairment can hardly see in dim environment or during night time. This due to vitamin deficiency is mostly treatable with vitamin supplement. Vitamin A helps in transfer of nerve impulses into image to retina. Some of the food with Vitamin A are eggs, cod liver oil, yellow and orange fruits and vegetables and so on.

Auditory nerve is not a part of the human eye. Explanation: Auditory nerve is a nerve bundle that transmits sound from cochlea to the brain. Cochlea is a auditory sense organ found at the back of each ears.

The shape of the lens is changed by ciliary muscles so that the image forms at a sharp focus at the retina. The lens becomes thicker to focus at near objects and becomes thinner to focus at distant objects.

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

According to the law of reflection, the angle of incidence is equal to the angle of reflection. If the incident ray makes an angle of 65 degree with the surface of plane mirror, than the angle of incidence can be calculated as: Angle of incidence = 90 – angle made with the plane mirror = 90 – 65 = 25 degree. Since, the angle of incidence is equal to the angle of reflection, therefore the required angle of reflection = 25 degree

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

In the human eye, when the light rays enter to a sharp focusing point on the retina. It acts as the film on camera. It receives the image and passes to cornea. Here, the internal lens of the eyes is focused by cornea. It transforms this image falling on the lens into electrical impulses. The electrical impulses are transferred to optic nerves which carry information to brain and we can see the object.

We can clearly view an object only when image is clearly reflected on retina. Our eyes focus distinct and near objects and reflects the image on retina. When eyes need to focus distinct object, then ciliary muscles reflex which increases the focal length. The eye lens converges the light and the objects are said to be unaccommodated. When eyes need to focus nearby object, then ciliary muscles relax which decreases the focal length. The eye lens diverges the light and the objects are said to be accommodated. The accommodation power of eyes is as close as 25 cm and as far as infinity.

The size of the pupil of the eye is adjusted by “Iris”. The pupil of our eye is an entrance for the light rays to enter our eyes and give us the sensation of sight. If too much light enters our eyes, it can be dangerous for eyes. Whenever the light is strong, the pupil shrinks in order to reduce the entrance of light and protect our eyes. If too less light enters our eyes, we don’t get a clear vision. Whenever the light is weak, the pupil expands in order to increase the entrance of light and improve the vision. This is how pupil of the eye changes its size to adjust for different amount of light.

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

The defect of an eye in which it cannot see the distant objects clearly is called myopia. A person with myopia can see nearby objects clearly.

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

The impression or sensation remains on the retina for about 1/16th of a second even after removal of the object.