Viva Voce: Image Formation by a Convex Lens | Lab Manuals for Class 10 PDF Download

Q.1. On what factor does the size of an image formed by a thin convex lens depend?

The size of an image depends on the position of an object from the lens.

Q.2. What is the nature of focal length of convex lens according to New Cartesian sign convention?

The focal length of convex lens is positive.

Q.3. What effect do you expect if the lens is thick?

Thick convex lens has shorter focal length so image distance will be reduced as compared to thin lens.

Q.4. Why is it preferred to perform this experiment in dark or shade?

To get sharp and distinct image of the candle flame, it is preferred to perform this experiment in dark or shade.

Q.5. A distinct image of the lighted candle has been obtained on the screen with fixed position using a thin convex lens. Why does the image of the candle get blurred, if the position of any one of them is slightly disturbed?

As we change the position of the object or lens, the image formed will be blurred, it is due to the rays which may meet before or after the screen.

Q.6. What will be the nature of image obtained on screen if a lower half of convex lens is covered with black paper?

The full size image will be obtained but with reduced brightness.

Q.7. What effect do you expect if the lens used to perform the experiment has scratches on it?

A sharp and distinct image will not be obtained accurately.

Q.8. How will you distinguish between a convex lens and a concave lens by holding in hand and looking the printed page through them? 

As concave lens cannot form enlarged image at any position of lens, so the lens which will form enlarged image of printed page, will be a convex lens.

Q.9. Why do we require a calm atmosphere to perform this experiment? 

We require a calm atmosphere so that flame becomes uniform throughout the experiment. Because it is difficult to measure flame height as well as image height of flickering plasma.

Q.10. A ray of light is passing through the principal focus of a convex lens. How will it emerge after refraction through the lens?

When a light ray passes through principal focus after refraction, it will be parallel to the principal axis.