A is a source emitting microwaves and B is a source emitting X-rays. The table suggests the frequencies for A and B.
Which row is correct?
|
Frequency emitted by A / Hz |
Frequency emitted by B / Hz |
A |
3 × 109 to 3 × 1011 |
> 1019 |
B |
1 × 1012 to 1 × 1013 |
3 × 1016 to 7.5 × 1020 |
C |
3 × 109 to 3 × 1011 |
3 × 1016 to 7.5 × 1020 |
D |
4 × 1014 to 8 × 1014 |
5 × 1013 to 7 × 1015 |
Answer: C
Step 1: Recall the wavelength ranges of microwaves and X rays:
- The wavelength range of microwaves is 0.1 m to 1 × 10−3 m
- The wavelength range of X rays is 1 × 10−8 m to 4 × 10−13 m
Step 2: Apply the wave equation to find frequency ranges:
- The speed of electromagnetic radiation is c , so to calculate frequency f use
- The frequency range of microwaves is
- This eliminates B and D because source A emits microwaves
- The frequency range of X rays is
- Both frequency ranges match option C