Suppose you have focused on a screen the image of candle flame placed at the farthest end of the laboratory table using a convex lens. If your teacher suggests you to focus the parallel rays of the sun, reaching your laboratory table, on the same screen, what you are expected to do is to move the:

• lens slightly towards the screen

• lens slightly towards the screen

• lens slightly towards the sun

• lens slightly towards the sun

In your laboratory you trace the path of light rays through a glass slab for different values of angle of incidence (i) and in each case measure the values of the corresponding angle of refraction (r) and angle of emergence (e). On the basis of your observations your correct conclusion is:

• i is more than r, but nearly equal to e
• i is less than r, but nearly equal to e
• i is more than e, but nearly equal to r
• i is more than e, but nearly equal to r

A student used a device (X) to obtain/focus the image of a well illuminated distant building on a screen (S) as shown below in the diagram. Select the correct statement about the device (X).

• This device is a concave lens of focal length 8 cm

• This device is a convex mirror of focal length 8 cm

• This device is a convex lens of focal length 4 cm

• This device is a convex lens of focal length 4 cm

A student obtains a sharp image of the distant window (W) of the school laboratory on the screen (S) using the given concave mirror (M) to determine its focal length. Which of the following distances should he measure to get the focal length of the mirror?

• MW

• MS

• SW

• SW

To determine the approximate value of the focal length of a given concave mirror, you focus the image of a distant object formed by the mirror on a screen. The image obtained on the screen, as compared to the object is always:

• Laterally inverted and diminished

• Inverted and diminished

• Erect and diminished

• Erect and diminished