1. Gamma rays are –
(a) streams of protons
(b) electrons and positrons
(c) streams of electrons
(d) electromagnetic radiation emitted in quantized units called photons
2. Beta rays are –
(a) high-speed electrons of positrons
(b) fast protony
(c) able to penetrate heavy armour plate
(d) electromagnetic waves
3. X-rays are –
(a) electromagnetic radiation of the same type as light, but of much shorter wavelength.
(b) electromagnetic radiation of the same type as light
(c) electromagnetic radiation
(d) The same as Gamma rays.
4. The breakdown of a sample of radioactive material-
(a) is always accompanied by gamma rays.
(b) can be speeded up by applying heat.
(c) goes at a rate characteristics of the kind of material.
(d) happens all at once for all the atoms.
5. Which particle can through the earth and also thousands of miles of solid lead without either losing energy or being stopped?
6. Protection against measles is possible when children are of-
(a) 3 to 6 months
(b) 6 to 12 months
(c) 3 to 9 months
(d) 9 to 12 months
7. The common harmless mosquito is known as –