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When light làlls on an object, it scatters even if the sunlight does not enter a room. due to scattered light., the object become visible.

1. An electric bulb 

2. Candle 

3. An oil lamp 

4. A torch

Incident ray, reflected ray and normal at the point of incidence all lie in the same plane. The angle of incidence is equal to the angle of reflection.

Correct answer is (c) Fire fly

Correct answer is (a) 8.33 min

Moon is non luminous body because it shines by reflecting the sunlight falling on it.

The bodies which emit light are called luminous bodies. 

Ex : Sun, stars, burning candle etc. 

The bodies which do not emit light are called non luminous bodies. 

Ex: Moon, earth, black board.

Correct answer is (d) Moon

(c) Periscope

(d) Can be smaller or bigger than the opaque object

• Image is virtual and erect. 
• Size of the image is equal to that of object 
• Image is laterally inverted. 
• The image formed by a plane mirror is always at the same distance as the object is in front of it.

To see the Solar Eclipse Safely: 

Take a cardboard or X-Ray film and make a small hole in it. Place it in front of a wall. Through the hole, the image of the Sun will be formed on the wall. This image we can see with a eye. We are not looking at the Sun directly, so there will be no harm to the eyes.

Objects that emit light on their own are called Luminous objects.

Virtual, enlarged and erect.

A solar eclipse occurs when the moon comes in between the Sun and the Earth and casts its shadow on the earth. In such a case, the moon being smaller in size casts its shadow only on a limited region on the earth.

Jugnu and firefly.

Glass, water, air etc.

The medium with higher refractive index in which speed of light is less is known as optically denser medium and the medium with lower refractive index in which the speed of light is more is known as optically rarer medium.

(a) Centre of curvature: It is the centre of the spheres of which the each surface of the lens forms a part. Represented bv C or 2f. 

(b) Principal axis: An imaginary straight line passing through the two centres of curvatures. 

(c) Optical centre: It is the central point of the lens. Represented by O. 

(d) Focus: The point at which rays of light parallel to principal axis converges (convex lens) or appears to diverge (concave lens) after refraction. Represented by F. 

(e) Focal length: The distance between focus and optical centre is called focal length. It is represented by f.

1. Optical fiber is a device that works on the principle of total internal reflection by which light signals (huge data) can be transmitted from one place to another place with a negligible loss of energy in a very short time.

2. It consists of a cable having one or more thin flexible fibers with a glass core through which light signals can be sent.

3. Optical fiber can be twisted and bent easily.

4. When a light a ray of light is incident at one end of the core of optical fiber, it suffers total internal reflection at the many places inside the fiber and emerges at the other end with negligible loss of energy.

5. The data or information in the form of pulses of light, can be sent through bundles of optical fibers.

6. Optical fibers have become very important in high-speed communications, such as cable TV and high-speed broadband services.Fiber optic cables are able to carry more signals than traditional copper cable telephone lines.

The shade of a tree is its shadow.

A substance through which light passes is called a transparent substance. 

Examples: glass, air, water etc.

(b) plane mirror

An inverted or an upside down image of the candle is seen on the diaphragm of the pinhole camera.

Luminous object.

1. Transparent objects — Those objects through which light can pass easily are called transparent objects, e.g. Water, glass, air.

 2. Translucent object— The object through which light can pass partially are called translucent object, e.g. tracing paper, waxed paper. 

3. Opaque object— The objects which do not allow the light to pass through are called opaque objects, e.g. wood.

The objects / materials through which light passes are said to be transparent.

(b) approaches a surface

Amedium which allows the passage of light through it easily, is called a transparent medium. 

Examples: glass, air, water etc.

(i) By applying oil, grease, butter on it or pasting a butter paper on it.
(ii) Grinding (rubbing) the surface of the glass by any abrasive material.

1. Transparent objects — Those objects through which light can pass easily are called transparent obj ects. e.g. Water, glass, air. 

2. Translucent object— The ohj ect through which light can pass partially are called translucent object, e.g. tracing paper, waxed paper. 

3. Opaque object— The objects which do not allow the light to pass through are called opaque objects, e.g. wood.

No, a transparent medium cannot form image. All the light that passes through a transparent medium completely pass through the substance. For the formation of image it is must that the light rays get reflected through the surface.

Correct answer is (d) clouds

The materials through which light does not pass are said to be opaque.

The shadows are long in the mornings and evenings and short in the afternoon.

The materials through which light passes partially are said to be translucent.

3. partial brightness

Umbra

1. It is the portion of shadow where no light reaches from the source of light due to the opaque object. 

2. It is completely dark.

Penumbra

It is the portion of shadow where a portion of light from the source of light reaches the shadow even in the presence of the opaque object in between them. It is not completely dark, but is dim (or less bright).

1. complete darkness

Light rays which travel from different directions to meet at a point are called as converging beam of light rays.