Define a ray.

Define wavefront and a ray.

Define decay constant of a radioactive sample. Which of the following radiations, alpha-rays, beta -rays, gamma -rays are similar to X-rays?

Define decay constant of a radioactive sample. Which of the following radiations, alpha-rays, beta -rays, gamma -rays are similar in nature to cathode rays?

Define decay constant of a radioactive sample. Which of the following radiations, alpha-rays, beta -rays, gamma -rays are easily absorbed by matter?

Define decay constant of a radioactive sample. Which of the following radiations, alpha-rays, beta -rays, gamma -rays travel with greatest speed?

(a) Define mineral. (b) Define Ore.

Define the following Ray?

Define the term 'focal length of a mirror'. With the help of a ray diagram, obtain the relation between its focal length and radius of curvature.