Table of Contents
Activity 11.9- Focusing Sunlight with a Convex Lens
Objective- To demonstrate how a convex lens can focus sunlight and explore the concept of light convergence.
Materials Needed-
- A convex lens (a lens that is thicker in the middle and thinner at the edges).
- A screen, like a piece of white paper.
- A sunny day (to have clear sunlight).
Safety Note- Be cautious when handling the convex lens in sunlight. The focused sunlight can be very intense and may cause burns or fire.
Also Check – Convex Lenses- Principles, Applications, and Insights
Procedure-
- Outdoor Setup- Take the convex lens and the screen outside on a sunny day.
- Hold the Lens to the Sun- Hold the convex lens towards the sun, allowing sunlight to pass through the lens.
- Find the Focus- Move the screen closer or further away from the lens until a bright spot of light (the focused sunlight) appears on the screen.
- Observe the Effects- Notice how the light converges to a point on the screen and the heat generated at that point.
Also Check – Class 7 Science -Chapter 15 – Light- Complete Notes
Also Check – Chapter 11- A Detailed Guide to the Light Activities for Class 7 Students
Core Concepts Explained-
- Convex Lenses and Light Convergence- Convex lenses are shaped to bend (refract) light rays so that they converge (come together) at a point known as the focal point.
- Focal Point- The point where the light rays meet after passing through the lens is the focal point. At this point, the light is most concentrated.
- Heat Generation- The convergence of sunlight at the focal point can generate significant heat, demonstrating the focusing power of the lens.
Also Check – Difference Between a Convex and Concave Lens
Possible Questions and Answers-
Why does the lens make the light come to a point?
- The shape of the convex lens causes the light rays to bend inward toward each other, focusing them to a single point.
Can we use any lens for this?
- No, you need a convex lens for this activity. Other types of lenses, like concave lenses, spread light rays apart instead of focusing them.
Is it dangerous to do this?
- It can be dangerous because the focused sunlight is very intense. It’s important to be careful and not to focus the sunlight on your skin or any flammable materials.
Why does it get hot at the focal point?
- When light rays converge, they bring their energy to a small area, which increases the intensity and heat at that point.
What happens if I move the screen away from the focal point?
- If you move the screen away from the focal point, the light spot will get larger and less intense, and the heat will decrease.
