A radioactive element has a half life of 4 days. The fraction that has decayed in 16 days is?
(15)/16
(1)/16
(3)/4
(1)/4
Correct answer is B
16 days = 4 half lives.
The fraction left 16 days = after 4 half live, = (1/2)4 = (1)/16.
One of the properties of gamma rays is that they are?
neutral
massive
positively charged
negatively charged
Correct answer is A
No explanation has been provided for this answer.
The battery connection that permits current to flow across a p-n junction is called?
reverse baised
forward baised
amplification
rectification
Correct answer is B
No explanation has been provided for this answer.
The process through which free electrons leave the surface of hot metal is known as?
photon emission
photo emission
thermionic emission
electron emission
Correct answer is C
No explanation has been provided for this answer.
1.3 x 10-15 Hz
3.1 x 1052 Hz
3.2 x 10-53 Hz
8.0 x 1014 Hz
Correct answer is D
E = hf
f = (E)/h
∴ f = (3.3 x 1.6 x 10-19)/6.6 x 10-34
= 0.8 x 1015 = 8.0 x 1014 Hz