Answer: P = I/c (intensity divided by speed of light).
- A P = I/c (intensity divided by speed of light)
- B P = Ic, multiplying intensity by the speed of light instead
- C P = I/c², dividing by the square of the speed of light
- D P = 2I/c, the value for a perfectly reflecting surface instead
Correct answer: A. P = I/c (intensity divided by speed of light)
Explanation: Radiation pressure P = I/c (for perfect absorption). For perfect reflection, P = 2I/c (momentum change is doubled as direction reverses). This pressure is extremely small but detectable.
In an electromagnetic wave, the oscillating electric field (E) and magnetic field (B) are perpendicular to each other and to the direction the wave travels - a purely transverse wave that needs no medium, unlike sound.
Concept context
Maxwell's equations, EM spectrum, properties, and applications of each band.