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1. It is an instrument used for viewing bodies or ships, which are over and around another body or a submarine. 

2. It is based on the principle of the law of reflection of light. It consists of a long outer case and inside this case mirrors or prisms are kept at each end, inclined L’9ht at an angle of 45°. 

3. Light coming from the distant body, falls on the mirror at the top end of the periscope and gets reflected 450 vertically downward. 

4. This light is reflected again by the second mirror kept at the bottom, so as to travel horizontally and reach the eye of the observer. 

5. In some complex periscopes, optic fibre is used instead of mirrors for obtaining a higher resolution. 

6. The distance between the mirrors also varies depending on the purpose of using the periscope.

The image which cannot get it on screen is called virtual image.

(c) plane mirror and convex mirror.

(c) Both the size and shape of the shadow of the tree change. 

No. We cannot catch our image on screep.

When we see our face in the mirror, the light reflected from our face falls on the mirror and gets reflected back again. Hence, we see our image in the mirror.

We cannot get the image formed by a plane mirror on the screen.

When a person finds it difficult to see nearby objects, he suffers from far sightedness or hypermetropia. This defect happens because of reduced curvature of lens. In this case, image of a nearby object is formed behind the retina. This defect is rectified by using a convex lens of suitable focal length.

When a person finds it difficult to see distant object, he suffers from near sightedness or myopia. Myopia happens because of increased curvature of lens. In this case, image of a distant object is formed before the retina. This defect is rectified by using a concave lens of suitable focal length. The lens helps in making the image on retina.

(b) He will clearly see a distant object

(c) Convex lens

1. Synthesis of colour is the method of creating colour by mixing various proportion of two (or) three distinct colours of light. 

2. These distinct colours are Red, Green and Blue called as primary colours.

1. When lighting a bulb in a dark room, light spreads the whole room quickly. 

2. This is because the light travels very fast. 

3. Light travels three lakh kilometers per second in air or vacuum. 

4. In theory, nothing can travel faster than light.

Light comes from different objects called sources, of light. 

Ex : 

Sun, candle, tube light.

(a) An image that cannot be obtained on a screen is called Virtual Image. 

(b) Image formed by a convex Mirror is always virtual and smaller in size. 

(c) An image formed by a Plane mirror is always of the same size as that of the object.

(a) An image which can be obtained on a screen is called real image. 

(b) An image formed by a concave lens cannot be obtained on a screen.

Characteristics of the image formed by a plane mirror:
1. Virtual and erect.
2. Behind the mirror.
3. Size of image is equal to size of object.
4. Laterally inverted image (image of left side visible on right side).
5. Distance of image behind the mirror is equal to distance of object in front of mirror.

(a) An image that cannot be obtained on a screen is called virtual image.
(b) Image formed by a convex mirror is always virtual and smaller in size.
(c) An image formed by a plane mirror is always of the same size as that of the object.
(d) An image which can be obtained on a screen is called a real image.
(e) An image formed by a concave lens cannot be obtained on a screen.

Characteristics of the image formed by a plane mirror. 

1. Virtual and erect. 

2. Behind the mirror 

3. Size of image is equal to size of object. 

4. Laterally inverted image (image of left side visible on right side) 

5. Distance of image behind the mirror is equal to distance of object in front of mirror.

The image, which cannot be obtained on a screen, is called virtual image. The images formed by plane mirror, convex mirror and concave lens are virtual.

The image, which cannot be obtained on a screen is called virtual image. The images formed by plane mirror, convex mirror and concave lens are virtual.

(a) We can obtain an enlarged and erect image by a convex mirror. (F)
(b) A concave lens always form a virtual image. (T)
(c) We can obtain a real, enlarged and inverted image by a concave mirror. (T)
(d) A real image cannot be obtained on a screen. (F)
(e) A concave mirror always form a real image. (F)

A, H, I, M, O, T, U, V, W and X are the letters. Which form same image as the letter is. These letters are laterally symmetrical.

A, H, I, M, O, T, U, V, W and X are the letters which form same image as the letter is. These letters are laterally symmetrical.

The image which cannot be taken on a screen is called a virtual image. When some object is placed very close to the concave mirror we don’t get any image on the white screen placed behind the mirror. Such an image is called a virtual image.

(a) False

(b) True

(c) True

(d) False

(e) False

Letters like A, H, I, M, O, T, U ,V, W, etc. appear the same when seen through a plane mirror.

1. The clear images are formed on plane surfaces. 

2. Faint or no images are formed on rough surfaces.

Characteristics of image by plane mirror: 

1. Object distance is equal to image distance. 

2. Size of the object is equal to size of the image. 

3. The image formed is always virtual and erect. 

4. Laterally inverted image is formed, (left and right alternates)

The objects which emit light i.e. which themselves are a source of light, are called luminous objects.

These are convex mirrors.

The objects that are not sources of light themselves are called as non-luminous objects.

Real image :

Type of image which can be obtained on a screen is called a real image.

Virtual image: 

An image which cannot be obtained on a screen is called a virtual image

(a) made of travelling in straight lines

(d) two images

Number of image n = \(\frac{360°}{θ} - 1\) = \(\frac{360°}{10°} - 1\)

= 36 - 1

= 35 images

Difference between the images formed in Pinhole camera and Plane mirror:

A. the pupil becomes larger 

When a person walks out of bright sunshine into a poorly lit room, the pupil dilates and becomes larger to allow maximum light to enter the eye and thus helps in viewing things easily in a poorly lit room.

The object distance is equal to image distance in a plane mirror. 

For the distance of man from his image to be 5m

The distance of man from mirror + distance of image from the mirror = 5m

Since object distance = image distance

Therefore, 2 distance of man from the mirror = 5m

Distance of man from the mirror = 5/2 = 2.5m

The man is 10m from the mirror at the starting, so he will have to walk 10 – 2.5 

= 7.5m towards the mirror for being 5m away from his image.