Light

Part of the eye which controls the light entering is called the iris. Iris controls the size of the pupil which regulates the amount of light entering into the eye.

We can see a non-luminous object when light is reflected from the object towards our eye. When the light strikes a non-luminous object and is reflected back to our eye, we are able to generate an image of it.

The laws of reflection still holds as long as the incident ray, the normal at the point of incidence and the reflected fray all lie in the same plane.

A is the correct answer because it is the only case where the angle of incidence is approximately equal to the angle of reflection as shown below: -

A is the correct answer because according to laws of reflection the angle of incidence is equal to the angle of reflection and it is obeyed only when we place our eye at the point A as shown below: -

The ray will be reflected from mirror A at 25^o and would strike the mirror B at 65^o and hence according to the laws of reflection would be reflected from mirror B at 65^o as shown in the figure below: -

Cones are the cells in our eyes which are sensitive to bright light and also senses colour whereas the rods are sensitive to dim light.

Cornea is the transparent front part of the eye.

The dark muscular structure know as iris is that part of the eye which gives colour to the eyes. It also controls the amount of light entering into our eye.

The impression of an image does not vanish immediately from our retina but persists there for 1/16 th of a second. So, if we move or hands at a rate faster than this then it will appear as moving in a blurred manner. This is what happening with Boojho as his fingers are appearing blurred due to the fast movement of his hand.

A ray of light will be reflected infinite number of times when two plane mirrors placed parallel and facing each other as each reflected ray would be the incident ray for the other mirror.

As angle of incidence is always equal to the angle of reflection. Hence if the angle between incident ray and reflected ray is 60° then the value of angle of incidence would be half of the angle between incident ray and reflected ray. So, the angle of incidence would be 30^o.

The distance between the mirror and the object is equal to the distance between the mirror and the image formed in the case of a plane mirror. Here, the distance between the object and its image formed by a plane mirror is 24 cm. Hence, the distance between the mirror and the object would be half of it which would be 12cm.

When a light gets dispersed it is broken down into its constituent colours, the combination of which forms the light as whole.

For example, the sunlight consists of seven colours hence, when it is dispersed by allowing it to pass through a transparent prism it is broken down into the seven colours.

The image of the child cannot be obtained on a screen as the image is being formed in a plane mirror and the images which are formed in a plane mirror are virtual in nature. Virtual images are those images which are not obtained on a screen.

Nocturnal birds are those birds which have the ability to see at night. As these birds have the ability to see at night it implies that they require a large amount of light to enter into their eyes so that they could see in the dim light. This is the reason why nocturnal birds have large cornea and a large pupil so that a large amount of light could enter into their eyes to enhance their night vision ability.

Our eyes have convex lens which is thicker at the middle.

It converges all the light that enters into our eyes and forms the image of the object at the back of the eye on a layer called retina.

The lens of the eyes gets affected if someone is suffering from cataract. If this happens the eyesight becomes foggy which is due to the reason that the lens becomes cloudy.

Cataract is treated by removing the opaque lens from the eye and then inserting a new artificial lens in its place.

(a) Three mirrors would be required by Boojho to see objects which he could not directly see. These mirrors would reflect the incident light successively so that the rays reach the position where the eye is being kept.

(b) The image indicating the position of the mirrors in the figure is as follows:

(c) He should place the mirrors at an angle of 45^o with respect to the incident light so that the angle between the angle of incidence and angle of reflection is 90^o and the ray of light is able to traverse the curvature of the apparatus which is at 90^o and reaches the eye of the observer.

(d) The direction of rays in the figure is shown in the diagram shown below: -

(e) If any of the mirrors is removed, he will not be able to see the objects as the incident rays will get deflected by the curvature of the pipe in random directions and all the incident rays would not be able to reach the eyes of the observer at the other end.

(a) The mistake in the above figure is that the direction of the propagation of the ray is wrong. In the diagram it is shown that the ray is propagating in the direction of reflected ray to the direction of the incident ray but the direction of propagation should be from the direction of incident ray to the direction of reflected as shown in the corrected figure below: -

(b) The mistake in the above figure is that it is not obeying the laws of reflection. It is not following the law that the angle of reflection is equal to the angle of incidence as in the above figure both the angles are not equal. Hence, the corrected figure with equal angle of incidence and reflection is as shown below: -

(c) The mistake in the above figure is the same as that of the previous one that it is not obeying the laws of reflection. It is not following the law that the angle of reflection is equal to the angle of incidence as in the above figure both the angles are not equal. Hence, the corrected figure with equal angle of incidence and reflection is as shown below: -

we know that the impression of an image does not vanish immediately from our retina but persists there for 1/16 th of a second. So, if we move still images of a moving object at a rate faster than this then the eye will perceive the object as moving. This is the phenomena which is being exploited in the process of carton film making. The still image of the objects in the cartoon films are played in a sequence at a rate faster than 16 images per second and our eyes perceive it as a moving picture.

Kaleidoscope uses the phenomena of multiple reflection where two or more plane mirrors are used in combination to make the different patterns of the desired object forming multiple images also. In a kaleidoscope two or more than two mirrors are belong arranged in a desired position with the definite angle of incidence so that the rays from the source gets reflected multiple number of times to reach the eye of the observer forming multiple images of different patterns.

Kaleidoscopes have a wide range of applications. They have an interesting feature of never forming the same pattern two times and a different pattern is formed each time. Designers of wallpapers, jewelry and fabrics and artists use kaleidoscope to get ideas for new patterns.

In a plane mirror the image formed undergoes lateral inversion that is the left side of the object appears on the right side of the image and the right side of the object appears on the left side of the image. Also, the image appears at the same distance behind the mirror as the object is being place in front of it. Keeping the above two rules in mind the diagrams showing the images formed by the word REST written in two ways in front of the mirror is as shown below: -

The names of the parts of the eye is as shown in the figure below: -