Human Eye and Colourful World — Science STD 10 — Question

An electric kettle consumes 1kW of electric power when operated at 220V. A fuse wire of what rating must be used for it?

Which of the following phenomena contributes significantly to the reddish appearance of the sun at sunrise or sunset?

1. Dispersion of light.
2. Scattering of light.
3. Total internal reflection of light.
4. Reflection of light from the earth.

A student determines the focal length of a device ‘X’ by focusing the image of a distant object on a screen placed 20cm from the device on the same side as the object. The device ‘X’ is.

If a magnification of, −1 (minus one) is to be obtained by using a converging mirror, then the object has to be placed:

1. Between pole and focus.
2. At the centre of curvature.
3. Beyond the centre of curvature.
4. At infinity.

For a healthy eye, the rays of light entering the eye form a sharp image on retina. For a myopic eye, the rays from distant objects focus in front of the retina forming a blurred image. Which of the following lenses shown below will help to correct myopia?

A student focussed the Sun rays using an optical device ‘X’ on a screen S as shown.

From this it may be concluded that the device ‘X’ is a (select the correct option)