# Concave mirror in Reflection of Light By Different Surfaces – Class 10 Science Experiment

## Activity Name: Concave mirror in Reflection of Light By Different Surfaces

### Activity Description:

In this experiment, you will use a concave mirror to understand its focusing properties. By allowing sunlight to fall on the mirror and using a small piece of paper, you will locate the point where the smallest and brightest spot (the image of the sun) is formed.

This point is known as the focus or focal point (F) of the concave mirror. You will also measure the distance of this spot from the pole of the mirror, which is the focal length (f). Additionally, you will learn that the radius of curvature (R) of the mirror is twice the focal length (R = 2f).

### Required Items:

1. Concave mirror
2. Sunlight source
3. Small piece of paper

### Step by Step Procedure:

1. Position the concave mirror in such a way that sunlight falls directly on it.
2. Take the small piece of paper and slowly move it in front of the mirror, paying attention to the spot where the smallest and brightest image of the sun is formed.
3. Ensure that the paper is small enough not to obstruct the incoming sun rays, allowing you to clearly see the focused spot.
4. Locate the point where the rays coming from the sun, parallel to the principal axis of the concave mirror, converge. This point is the focus (F) of the mirror.
5. Measure the distance of the focused spot from the pole of the mirror. This distance is the focal length (f) of the concave mirror.
6. Calculate the radius of curvature (R) of the mirror by using the formula: R = 2f.

### Experiment Observations:

• The smallest and brightest spot formed when the paper is moved in front of the concave mirror represents the focused image of the sun.
• The point where the rays parallel to the principal axis converge is known as the focus (F) of the concave mirror.
• The distance from the focus to the pole of the mirror is the focal length (f).
• The radius of curvature (R) of the concave mirror is twice the focal length (R = 2f).

### Precautions:

1. Do not look directly at the sun or its reflection on the mirror to avoid eye damage. Use indirect methods to observe the focused spot.
2. Ensure that the paper used to find the focused spot is small enough not to block the incoming sun rays completely.

### Lesson Learnt from Experiment:

Through this experiment, you have verified the focusing properties of a concave mirror. The concave mirror converges parallel rays of light to a specific point called the focus. The distance from the focus to the pole of the mirror is known as the focal length, and the radius of curvature is twice the focal length.