Question
An electromagnetic wave has a wavelength of 2.1 cm in a vacuum.
Which region of the electromagnetic spectrum contains this wave?
(A) infrared
(B) microwave
(C) radio wave
(D) visible light
Answer/Explanation
Ans: B
Question
A beam of visible light is in a vacuum.
What could be the frequency of the light?
(A) $5.0 × 10^{5}Hz$
(B) $5.0 × 10^{8}Hz$
(C) $5.0 × 10^{11}Hz$
(D) $5.0 × 10^{14}Hz$
▶️Answer/Explanation
Ans: D
Question
Some sources of electromagnetic waves in free space are listed.
1 a radio wave transmitter
2 a source of X-rays
3 a 30 mm wavelength radar transmitter
4 a light-emitting diode that emits red light
Which list gives the sources in order of increasing wavelength, from left to right, of the waves emitted by the sources?
(A) 1 → 3 → 4 → 2
(B) 2 → 4 → 1 → 3
(C) 2 → 4 → 3 → 1
(D) 3 → 1 → 4 → 2
▶️Answer/Explanation
Ans: C
Question
Two wave sources emit coherent waves. Which condition must be correct for the coherent waves?
A The waves are emitted in phase.
B The waves are emitted and move in opposite directions.
C The waves are emitted with a constant phase difference.
D The waves are emitted with the same amplitude.
▶️Answer/Explanation
Ans C