1. An object of height 5 cm is placed perpendicular to the principal axis of a concave mirror of focal
length 10 cm. If the distance of the object from the mirror is 20 cm, determine the position, nature and
size of the image formed.
[3]
2. A convex lens has a focal length of 15 cm. At what distance should an object be placed from the lens
so that it forms an image at 10 cm from the lens? Also, find the magnification produced by the lens.
[3]
3. Light enters from air to glass having refractive index 1.50. What is the speed of light in the glass?
The speed of light in vacuum is $3 \times 10^8 \text{ ms}^{-1}$.
[2]
SECTION B: ELECTRICITY
4. A copper wire has a diameter of 0.5 mm and resistivity of $1.6 \times 10^{-8} \Omega \text{ m}$. What
will be the length of this wire to make its resistance $10 \Omega$? How much does the resistance change
if the diameter is doubled?
[4]
5. An electric heater of resistance $8 \Omega$ draws 15 A from the service mains 2 hours. Calculate the
rate at which heat is developed in the heater.
[2]
6. Two lamps, one rated 100 W at 220 V and the other 60 W at 220 V, are connected in parallel to
electric mains supply. What current is drawn from the line if the supply voltage is 220 V?
