Question

which of the following statements are true?
choose all answers that apply:
a all em radiation travels at the speed of light in a vacuum.
b human eyes can see the entire em spectrum directly.
c em radiation consists of oscillating electric and gravitational fields.
d em radiation has both wave and particle properties.

Explanation:

• Statement A: According to the theory of electromagnetism, all electromagnetic (EM) radiation travels at the speed of light (\(c = 3\times10^{8}\space m/s\)) in a vacuum.
• Statement B: Human eyes can only see a small portion of the EM spectrum called the visible spectrum (wavelengths approximately from \(380 - 750\space nm\)). There are many parts of the EM spectrum (such as radio waves, X - rays, gamma rays) that are not visible to the human eye.
• Statement C: EM radiation consists of oscillating electric and magnetic fields (not gravitational fields). The electric and magnetic fields are perpendicular to each other and also perpendicular to the direction of propagation of the EM wave.
• Statement D: EM radiation has a dual nature. It can exhibit wave - like properties (such as interference, diffraction) and particle - like properties (photons, which are discrete packets of energy).

Answer:

A. All EM radiation travels at the speed of light in a vacuum.
D. EM radiation has both wave and particle properties.