• As a mirror reflects light, an image of the object that is ahead of the mirror is formed on it.
• The image of an object can be defined as the impression of the object created by the light in the mirror.
• The gap between the image and the mirror, and the object and the mirror at all times remain the same.
• When the distance between the item and the mirror is increased or decreased, the distance between the image and the mirror is similarly increased or decreased.
• However, the size of the image formed on the mirror can vary concerning the distance between the object and the mirror.
• If space between the object and the mirror increases, the size of the image decreases and vice-versa.
• An image is said to be erect if the image is formed on the same side up as that of the object.

The image will be called Inverted if it is formed upside-down, set side by side to the object.

Left-right inversion of the image.

The image formed by the mirror is always left-right inverted. This means that the right side of the object appears on the left side of the image, and the left side of the object appears on the right side of the image.

Why is the word ‘AMBULANCE’ painted on an ambulance left-right inverted?

This is because of the upside-down left-right image on a mirror. The word ambulance written as left-right inverted would be read easily by the driver of the vehicle ahead of the ambulance in its rear-view mirror. The rear-view mirror will again upturn the word left-right wise.

• Incident Ray - The light ray that falls on the reflecting surface is called an Incident Ray.
• Reflected Ray - A Reflected Ray is a light ray that is reflected from a reflecting surface.

Normal- At the point of incidence of Incident Ray, the normal is a line that is perpendicular to the reflected plane.

Types of Reflection

Depending upon the surface of the reflecting object, the reflection of light may differ.

• Diffused Reflection or Irregular Reflection: In this type of reflection, the light rays that fall on the surface are reflected in different directions asymmetrically. This generally happens in the case of a non-uniform or roughly surfaced object.
• Regular Reflection: In this type of reflection, the light rays that fall on the surface of the reflecting object reflect in a specific direction. The reflected rays are always collateral to each other. This normally happens in the case of an even and glossy surface.

A spherical mirror is a mirror that has a sphere-like shape. It seems as if it is a part of a sphere. There are two kinds of spherical mirrors:

• Concave Mirror - It is a spherical mirror whose reflecting surface is curved within.
• Convex Mirror - It is a spherical mirror whose reflecting surface is curved externally.

The Image formed by a Concave and Convex Mirror

An image can be of two types:

Real Image	Virtual Image
The real image is formed when the light rays reflect and converge at the same point.	When light rays reflect and separate from the same place, a virtual image is created.
It can be observed on a screen.	It cannot be observed on the screen.
It is always inverted.	It is always perpendicular.
It is formed by a concave mirror	It is formed by Concave, Convex, and Plane Mirrors

 

A lens is a part of a reflecting material like glass but curved from two sides. Lenses are different from mirrors that have a reflecting surface only on one side. Depending upon its shape a lens can be classified as

• Convex Lens - A Convex Lens bends outwards. It is thicker in the middle and narrows down at the edges. It unifies the light rays passing through it at a specific point. Therefore, it is also known as a Converging Lens.
• Concave Lens - A Concave Lens bends inwards. It has broader edges and a narrow center. It reflects the light that travels through it in divergent directions. Therefore, it is also known as a Diverging Lens.

Images formed by Convex and Concave Lenses

A Convex lens forms an image that is:

• real
• inverted
• the image is enormous and emerges close to the lens

A Concave lens forms an image that is:

• virtual
• erect
• small and appears far away

What is a Rainbow?

• A rainbow is a natural phenomenon that occurs when the sun's light rays are reflected and refracted by water droplets in the atmosphere.
• A rainbow appears as a curve on the sky that contains a band of seven colours – Red, orange, yellow, green, blue, indigo, and violet.
• The white light of the sun contains seven coloured lights in it that disperse out due to refraction (called a Spectrum of Lights). This spectrum of white light can be seen in Rainbows, Soap bubbles, the surface of a CD or 

Newton's Disc

• Newton’s disc can be obtained by dividing a disk into 7 split-up and painting each of them with the seven colours of the rainbow.
• When the disc is rotated quickly in daylight, all the colours tend to blend together, making the disc appear whitish.

Q1. State the characteristic of the image formed by a plane mirror.

Ans: Characteristics of an image formed by a plane mirror are:

• The image distance is equal to the object distance. 
• Image height is equal to object height. 
• The image is virtual and erect.

Q2. What is a virtual image? Give one circumstance where a virtual image is formed.

Ans: Virtual image: When light rays seem to originate at a spot but do not intersect, a virtual image is created. It is visible to human eyes. As a result, rear-view mirrors generate virtual images. The circumstances where a virtual image is formed:

• It is formed when reflected rays seem to meet.
• Such images cannot be acquired on the screen.
• Virtual images are always formed in the convex mirror and plane mirror.

Q3. Give one advantage of a concave and a convex mirror.

Ans: Advantage of the concave and convex mirror: 

• Concave mirror – used as a reflector in a torch.
• Convex mirror – used in vehicles as a rear-view mirror.

Q4. What type of lens always creates a real image?

Ans: Neither concave nor convex lens at all times forms a real image. A convex lens forms both real and virtual images. A concave lens creates virtual, erect, and diminished images.

Q5. What type of lens always creates a virtual image?

Ans: The type of lens which always creates a virtual image is:

• A concave lens always creates a virtual image. 
• After the rays are refracted, they never meet and hence there will be no real image.