Keep a spent tubelight in a dark place. Rub it vigorouly with a thin polythene bag. What happens ? Why?

Take a plastic boat and make a hole at this rear end. Inflate a balloon and fix it on the hole in the boat. Release the boat in water. What happens to the boat as the air in the balloon escapes slowly? Why?

What is lake tapping ? Why it takes place?

A closed bottle containing water at 30^@C is carried to the moon in a space-ship. If it is placed on the surface of the moon, what will happen to the water as soon as the lid is opened?

The work function for the following metals is given Na: 2.75 eV, K:2.30 eV , Mo: 4.17 eV , Ni: 515 eV. Which of these metals will not give photoelectric emission for a radiation of wavelength 3300 A from a He-Cd laser placed 1m away from the photocell? What happens if the laser is brought nearer and placed 50 cm away?

At least a small quantity of garbage or waste is produced every day in each house. What will happen if you keep this garbage for many days in your house?

Take some water in a pot and add few pieces of ice to it . Observe what happens . Why do we see the ice float on water ?

Use your brain power At least a small quantity of garbage or waste is produced every day in each house. What will happen if you keep this garbage for many days in your house?

A 4.5 cm needle is placed 12 cm away from a convex mirror of focal length 15 cm. Give the location of the image and the magnification. Describe what happens as the needle is moved farther from the mirror.

Observe your mother while she elephant's foot (Amorphophallus) or arum leaves. Your hands may also begin to itch if you try to cut these leaves. Why does this happen? Try to find out. Ask your mother what she does to prevent the itching.