Q: State the laws of reflection. Draw a diagram to show incident and reflected rays.

First, we consider reflection, as shown in the diagram below for a light wave striking a surface. We identify the incoming ray as the incident ray and the outgoing ray as the reflected ray. Concomitantly, the angle\$\theta_i\$ that the incoming ray makes with a line (dashed in the diagram) normal to the surface is called the angle of incidence. The angle \$\theta_r\$ for the reflected ray is called the angle of reflect. The law of reflection states that the angle of incidence is equal to the angle of reflection, or, stated mathematically.And also the incident ray, the reflected ray, and the normal to the surface of the mirror all lie in the same plane.

Question 1

State the characteristics of the image formed by a plane mirror.

Accepted Answer

(i) Plane mirror forms an erect image.(ii) It forms a virtual image.(iii) Size of the image is same as that of the object.(iv) Image is formed at the same distance behind the mirror as the object stands in front of it.(v)Image formed is a laterally inverted image i.e., right hand side of the object seems to be the left hand side and vice-versa.

Question 2

Describe an activity to show that the incident ray, the reflected ray and the normal at the point of incidence lie in the same plane.

Accepted Answer

Place a plane mirror on the table. Take a paper sheet and make a small hole in its center. Make sure that the light in the room is not bright. Hold the sheet normal to the table. Take another sheet and place it on the table in contact with the vertical mirror. Draw a normal line on the second sheet from the mirror. Now, light a torch on the mirror through the small hole such that the ray of light falls on the normal at the bottom of the mirror. When the ray from this hole is incident on the mirror, it gets reflected in a certain direction. You can easily observe the incident ray, reflected ray and the normal to the mirror at the point of incidence on the sheet placed on the table. This shows that the incident ray, the reflected ray, and the normal to the surface at the point of incidence all lie in the same plane.

Question 3

Angle of incidence is equal to the angle of reflection. This is true :

Accepted Answer

By laws of reflection, angle of incidence is equal to the angle of reflection. Note that they may appear as unequal when surface is rough. However on a rough surface, due to the changes in the surface boundaries it appears unequal. At actually small surface area, angle of incidence equals the angle of reflection.

Question 4

A light ray is incident normally on a plane mirror.(a) What is the angle of incidence?(b) What is the path of reflected ray?

Accepted Answer

Case (a):If a ray of light is incident normal to the surface of the plane mirror, then the angle of incidence is $0^0$, as the normal passes perpendicularly to the mirror.Case (b):The Second Law of Reflection states that the angle of incidence is always equal to the angle of reflection. Therefore, the angle of reflection is same as the angle of incidence, that is, $0^0$. So, the reflected ray will retrace the path of  the incident ray.

Question 5

What is reflection? Write the laws of reflection.

Accepted Answer

Reflection: The process of sending back the light rays which fall on polished surface is called reflection of light.Laws of reflection:(i) The angle of reflection is always equal to the angle of incidence.(ii) The incident rays, reflected rays and the normal, all lie in the same plane.

Question 6

Draw a ray diagram showing the formation of Image of a point object by a plane mirror.

Accepted Answer

showing the formation of image of a point object by a plane mirror.

Question 7

What is reflection? Give two examples.

Accepted Answer

A phenomenon of returning light from the surface of an object when the light is incident on it is called reflection of light.Examples:Reflection by a plane mirror.Reflection by a spherical mirror.

Question 8

Under what condition in an arrangement of two plane mirrors, incident ray and reflected ray will always be parallel to each other, whatever may be angle of incidence. Show the same with the help of ray diagram.

Accepted Answer

When two plane mirrors are placed at right angle to each other, then the incident and reflected rays will always be parallel to each other.

Question 9

State the laws of reflection. Draw a diagram to show incident and reflected rays.

Accepted Answer

First,&#10;we consider reflection, as shown in the diagram below for a light wave striking&#10;a surface. We identify the incoming ray as the incident ray and the outgoing&#10;ray as the reflected ray. Concomitantly, the angle$\theta_i$  that&#10;the incoming ray makes with a line (dashed in the diagram) normal to the&#10;surface is called the angle of incidence. The angle $\theta_r$  for&#10;the reflected ray is called the angle of reflect.&#10;&#10; The law of reflection states that the angle of incidence is equal to the angle of reflection, or, stated mathematically.And also the incident ray, the reflected ray, and the normal to the surface of the mirror all lie in the same plane.

Question 10

Describe an experiment to verify the laws of reflection of light.

Accepted Answer

Laws of reflection.  (i) The incident ray, the reflected ray and the normal at the point of incidence, lie in the same plane. (ii) The angle of Incidence and angle of reflection are equal I.e. $\angle i = \angle r $. Verification Take a wooden drawing board and fix a white sheet of paper on it. In the middle of paper draw a straight line KK\ Mark a point B on it. Draw a perpendicular BN. Place a mirror XX' on line KK' such that the polished side of the mirror is along the line. Hold the mirror in the mirror holder.Fix two steel pins P and Q on the straight line AB at least 10 cm apart. Look for the images of the pins P and Q and fix two pins P a such that P', Q', and images of P and Q are all in the same straight line. Remove the pins and draw small circles around the pinpricks. Remove the mirror also. Join P'Q' and produce the straight line to meet at B. Measure $\angle ABN$ = i and $\angle CBN$ = r. It is found that $\angle i = \angle r$. This proves that the Angle of Incidence is equal to the Angle of Reflection. As the incident ray, the reflected ray and the normal lie in the plane of the paper, therefore, they lie in the same plane.

Revise with Concepts

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Reflection Due to Bending of Light