13.
Electromagnetic radiations are given our due to
Answer : D. None of these
14.
Polarids are used in
Answer : B. photo-elasticity
15.
Consider the statements: X -rays I. are not electromagnetic radiations II. Are electromagnetic radiations III. Have longer wave lengths IV. Have shorter wave lengths of these points
Answer : C. II and IV are correct
16.
Consider the following statements: Radioactive substances emit I. Alpha rays II. Beta rays III. X-rays rays IV. Gamma rays
Answer : C. I,II and IV are correct
17.
X-rays cannot penetrate through
Answer : C. lead
18.
The transverse wave nature of light was proved by
Answer : C. Polarisation