Theory & Procedure, Reflection in Concave Mirror | Science Class 10 PDF Download

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OBJECTIVE

To study reflection in concave mirror and observe image formations for different positions of the object.

Related terms:

Reflection:
Whenever light, travelling in one medium, comes in contact with surface of another medium, a part of it is returned into the first medium. The phenomenon of returning of light into first medium is known as reflection of light.

Concave mirror:
A concave mirror is that spherical mirror in which the reflection of light takes place at the concave surface i.e. bent-in surface.

Pole:
It is the center of the reflecting surface of the concave mirror also called vertex of mirror, generally denoted by letter ‘P’.

1. Center of curvature:
   It is the center of that sphere of which the concave mirror forms a part, denoted by letter ‘C’.
2. Principal axis:
   The straight line passing through the center of curvature and pole of  concave mirror is called its principal axis.
3. Principal focus:
   A beam of light incident parallel to the principal axis, after reflection from the spherical mirror, either actually converges to or appears to diverge from a fixed point on the principal axis. The fixed point is called the ‘Principal focus’, denoted by letter 'F'.
4. Laws of Reflection:
   1)    The angle of incidence is equal to the angle of reflection.
   2)    The incident ray, the reflected ray and the normal at the point of incidence, all lie in the same plane. 
5. Types of images:
   1)    Real image: If the reflected rays actually meet at a point, then the image formed is real. It can be obtained on screen.
   2)    Virtual Image: If the reflected rays do not actually meet at a point but appear to diverge from a point, then the image formed is virtual.

As performed in the lab:

Materials required:

A concave mirror, a mirror holder, a semi transparent screen fixed to a stand and a small candle with stand.

Procedure

• Fix the concave mirror in the mirror holder and place it on edge of the table.
• Mount a small candle vertically on a stand. Place it in front of the concave mirror on the left hand side (i.e. shiny surface) say on focus 'F'.
• Place the screen such that the lower level of screen must be so arranged that it remains just above the principal axis of the mirror. 
• Locate a sharp image of candle by adjusting the position of the screen. Note and record the position and nature of the image formed on the screen. 
• Repeat the experiment by placing candle at different positions as mentioned in observation table [Table 1] below.

Table 1: Observation table

As performed in the simulator:

• Select "Show Labels" checkbox to view all labels in the simulation.
• Select "Show Help" checkbox to view help to use the simulation.
• Drag the "Object" (candle) along principal axis by clicking on blue point over the candle and observe the nature of the "Image" being formed.
• Select "Show Rays" checkbox to see how the image gets formed. 
• Place the object at different positions (as mentioned in the observation table [Table 1] given above) and note down the observations in the observation table by clicking on "Observation" tab.
• Click on Submit, to verify your observations. Correct observations will be highlighted in green, and incorrect ones will be highlighted in red.