Which statement about electromagnetic waves is correct?
Correct Answer: \( \boxed{\mathrm{A}} \)
A wavelength of \(5.0\times10^{-6}\,\mathrm{m}\) (\(5\,\mu\mathrm{m}\)) lies in the infrared region, which is invisible to the human eye.
All electromagnetic waves travel at the same speed in free space, they can be polarised, and they are oscillations of electric and magnetic fields rather than vibrating atoms.
Therefore, the correct answer is (A).
Which row correctly identifies the properties of all electromagnetic waves?
| Transverse wave | Longitudinal wave | Can travel in free space | |
| (A) | ✓ | ✗ | ✓ |
| (B) | ✓ | ✗ | ✗ |
| (C) | ✗ | ✓ | ✓ |
| (D) | ✗ | ✓ | ✗ |
Correct Answer: \( \boxed{\mathrm{A}} \)
All electromagnetic waves are transverse waves and can propagate through a vacuum (free space).
They are not longitudinal waves, so only row (A) correctly lists all their properties.
Therefore, the correct answer is (A).
What is the approximate range of wavelengths in free space for infrared radiation?
Correct Answer: \( \boxed{\mathrm{D}} \)
Infrared radiation lies just beyond the red end of the visible spectrum.
Its wavelength range is approximately \(800\,\mathrm{nm}\) to \(1000\,\mathrm{\mu m}\) (or \(1\,\mathrm{mm}\)).
The other ranges correspond to ultraviolet, radio waves, and visible light.
Therefore, the correct answer is (D).
