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The formula to calculate the no. of images of an object placed between 2 plane mirrors – (360/θ) − 1; where theta is the angle of inclination.

a- 2 (360/120) – 1 = 3 – 1 = 2

b- 7 (360/45) – 1 = 8 – 1 = 7

c- 1 (360/180) – 1 = 2 – 1 = 1

d- 5 (360/60) – 1 = 6 – 1 = 5

e- 3 (360/90) – 1 = 4 – 1 = 3

Infinite number of images of the candle will be formed because the mirrors are placed parallel to each other.

Shadow: When light fall son an opaque object, light is obstructed and a dark patch on a screen kept behind is called shadow. This is because light propagates in straight line. If distance between object and screen is less, the shadow will be (umbra) dark and smaller. If the distance is increased shadow will be dim and larger. 

Conditions Required for a shadow to form are:

1. There should be a source of light. 

2. An opaque object. 

3. A screen. 

4. The opaque object is placed between the source of light and the screen.

Myopia (nearsightedness) is the defect of vision wherein a person is unable to see the distant objects clearly as the light is unable to focus on the retina and thus distant objects appear to be blurred. The problem of nearsightedness is that the light is focused in front of the retina

Myopia is corrected by wearing glasses or contact lenses. A concave lens(diverging lens) with a minus power is used in the glass, which moves the image back to retina and thus clears the image. The diverging lens will diverge the light before it reaches the retina. The light will then be converged by cornea and lens thus producing an image on the retina.

The two types of reflection of light are Regular reflection of light and Diffused reflection of light.

Regular reflection of light makes us see an object from all directions as the reflected rays are all parallel and in a particular direction so the image of the object can be viewed from all directions. In diffused reflection of light the reflected rays are neither parallel nor in a specific direction so the image of the object isn’t visible from any direction.

We are able to see the moon because the light of sun falls on moon and is reflected onto the earth. Hence, we are able to see the moon.

Yes, I have observed the arrangement of plane mirrors in a sweet shop. So many images are formed.

Real and inverted image. If the object is placed very close to the mirror then the image is virtual and erect.

Prism is a triangular piece of glass that splits white light to different colours.

Light is a form of Energy i.e. The external physical cause that affects our eye to produce the sensation of vision.

Man-made objects which emit light are artificial sources of light.

Sun, stars,jugnu, firefly.

Sun, stars,jugnu, firefly.

The crystalline lens provides the proper focal length so that image of objects at different distances formed on the retina.

Human eye have crystalline lens called convex lens.

Difference Between 

Luminous 

Luminous The bodies which have light of their own e.g. sun stars, bulb, candle, oil lamp, torch, a lantern. 

Non-Luminous 

The bodies-which do not have their own Iight.e.g. moon, chair, table. When light falls on them, they become visible.

The human eye has convex type of lens. Light that hits the lens of the eye is focused by the lens so that it hits the retina. Retina has photoreceptor cells (rods and cones) which get stimulated and sends signals to the brain for viewing.

A Kaleidoscope is a toy mostly used by children for enjoyment. It is made of a tube with plain mirrors and colored glass pieces inside it at one of the end.

Kaleidoscope having object chambers are used for hiding valuables.

When a beam of sunlight is passed through a glass prism, it splits up into a band of 7 colors, also known as a spectrum.

A Glass Prism. It is a device used to split white light into seven colors. It has 2 triangular ends and 3 rectangular sides which help in splitting the white ray of light into a band of 7 colors, also known as spectrum.

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

Non- luminous objects are those that are themselves not capable of producing their own light but can reflect light from another source. 2 non luminous objects are wood, plastics etc.

Moon also is incapable of producing its own light and it reflects sunlight and hence is non-luminous.

Objects that have their own light i.e., objects that emit light of their own are known as luminous objects. 2 luminous objects are- stars and sun.

The sun and the stars have their own light. A light bulb is also luminous.

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.

Example: The images are reversed by the plane mirror.

Night blindness is the inability to see properly at night or in poor light. In scientific terms, it is called as “nyctalopia”.

The following factors cause night blindness:

1. The deficiency of Vitamin A (retinol) in the diet of a person for a considerable time can lead to the disease called night blindness. 

2. The disorder in which the rod cells in the retina gradually lose their ability to respond to the light. 

3. It can also happen due to cataract, or clouding of the eye’s lens. 

4. Usher syndrome can also cause night blindness, which is a genetic condition that affects both hearing and vision. 

5. Nearsightedness or blurred vision can also cause night blindness.

White light (say, sunlight) consists of seven colors can be shown by passing this light through a prism. The sunlight passes through the prism and splits into a band of 7 colors, also known as the spectrum.

Dispersion of light is the separation of white light or visible light into different colors is known as dispersion.

Formation of rainbow is a natural phenomenon which is caused by the dispersion of sunlight in the sky. The sunlight splits into 7 colors, namely, violet, indigo, blue, green, yellow, orange and red.

The phenomenon which enables us to see movies in a cinema hall is known as Persistence of Vision. The property of this phenomenon is that the image formed on the retina of the eye persists for about 1/16th of a second, hence if 16 frames are shown on a screen in succession, they are viewed by the retina as an ongoing action.

C. vitamin A 

Vitamin A deficiencies occur from fat malabsorption, liver disorders and inadequate food intake.

The information that we get about sunlight from the formation is about dispersion of light. The separation of white light into seven different colors is known as dispersion.

Deficiency of Vitamin A in the diet causes night blindness.

Vitamin A helps in transforming the nerve impulses into images in the retina. Deficiency of vitamin A (also known as retinol) causes night blindness. Night blindness is the inability to see properly at night or in poor light.

A rainbow is a spectrum of sunlight. By seeing a rainbow we come to know that sunlight is consist of any colours.

We can say that sunlight = (Red + orange + yellow + green + blue + indigo + violet) here we only consider the basic colour.