The speed of light in air is:

1. 3 x 10⁸ m s^-1
2. 330 m s^-1
3. 5100 m s^-1
4. 3 x 10¹⁰ m s^-1

What causes sound?

There is no atmosphere on moon. Can you hear each other on the moon’s surface?

Choose the correct word/words to complete the following sentence —

When sound travels in a medium ………. (the particles of the medium, the source, the disturbance, the medium) travels in form of a wave.