Science questions in short. [2 marks ]

The iris adjusts the size of pupil according to the light of varying intensity. When the amount of light is very high, the iris contracts the pupil and reduces the amount of light entering the eye. Whereas, when the amount of light is less, the iris expands the pupil so that more light can enter the eye and things can be viewed clearly.

The phenomenon is known as Lateral inversion. The effect produced by a plane mirror in reversing the images from left to right and right to left while forming images is lateral inversion.

The eye lens is made up of living cells and the focal length of eye lens is adjustable. Whereas, an ordinary convex lens is made of glass and its focal length cannot be changed as it is fixed.

In dim light the size of the pupil of our eye becomes larger or dilates to increase the amount of light going inside the eye. This dilation in size is facilitated by the muscles of iris.

A book lying on a table in a room can be seen from all the parts of the room because of reflection by the light falling on the book. The light is reflected by the book and it reaches our eye at any part of the room.

The image of an object in a plane mirror is virtual. Virtual image cannot be projected onto the screen because it is not real. A virtual image is a copy of the object, formed on the plane mirror. The light rays never come from the image. They appear to come from the object.

Diffuse reflection of light takes place. Surface of cardboard in not smooth. Law of reflection doesn't hold.

The pupil regulates the amount of light entering the eye. However, the size of the pupil is controlled by the Iris. So, we can say that the iris controls and regulates the amount of light entering the eye.

In bright light the size of the pupil of our eye constricts and becomes small to reduce the amount of light going inside the eye. This reduction in size is facilitated by the muscles of iris.

The light ray reflected by a surface, when an incident ray strikes the same surface is the reflected ray. The reflected ray corresponds to the incident ray always.

Diffused reflection takes place from a rough surface. The reflected rays are not parallel in diffused reflection. Regular reflection takes place from a smooth surface. The reflected rays are parallel in regular reflection.

Light is split into its constituent colours, when it gets dispersed, e.g. Rainbow formation is due to the dispersion of white light after passing through water droplets.

When a ray of light is incident normally (perpendicularly) on a plane mirror, the ray reflects and follows the same path.

The apparatus used to obtain a thin beam of light is known as Ray box. The rays are bright enough to be viewed easily. A ray box is a standard source of light used in optics experiments.

In bright sunshine the size of the pupil of the eye is very small so when we enter a darkened cinema hall from bright sunshine very little amount of light enters the eye. The vision improves at some time later because the pupil dilates and more amount of light enters the eye easily.

Cornea is the transparent front part of an eye. It covers the front portion of the eye.

For a single incident ray falling on a plane mirror, there is always a single reflected ray. The angle of incidence is always equal to the angle of reflection, this is by the law of reflection.

Iris is the part of the eye which gives its distinctive colour.e.g. If a person is said to have blue eyes, then that actually refers to the blue colour of the iris.

Blind spot is the point in human eye where the image is not visible. This is because there are no photoreceptors, i.e., rods and cones present in the optical disk.

The rainbow is usually seen after heavy rainfall because after a rain shower, there are droplets of water in air, when sunlight passes through these water droplets, it splits into seven colours and forms rainbow.

Normal is an imaginary line perpendicular to the surface, in the reflection of light from a plane mirror.

Rods are rod shaped cells present in the retina are sensitive to dim light. They are most important for vision in dim light. Cones are cone shaped cells present in the retina are sensitive to bright light. These photoreceptor cells are responsible for color vision.