Light & the Electromagnetic Spectrum — Drills · Grade 12 Science
Chapter: Waves, Sound & OpticsWhat these drills covers
By the end of Light & the Electromagnetic Spectrum you should be able to:
- I can describe light as an electromagnetic wave and order the spectrum by wavelength, frequency, and energy using c = f λ.
- I can explain wave-particle duality and calculate a photon's energy with E = h f.
6 questions, multiple choice, numeric and written answer, each with a worked explanation.
Vocabulary used: electromagnetic (EM) wave, electromagnetic spectrum, speed of light (c), photon, wave-particle duality, Planck's constant (h).
Problem 1
- electromagnetic
- pressure
- longitudinal
- sound
Answer and explanation
electromagnetic
Light is an electromagnetic wave of oscillating electric and magnetic fields, needing no medium.
Problem 2
- gamma rays
- radio waves
- visible light
- X-rays
Answer and explanation
radio waves
Radio waves sit at the long-wavelength, low-energy end of the electromagnetic spectrum.
Problem 3
Answer and explanation
0.1 m
λ = c ÷ f = (3 × 10⁸) ÷ (3 × 10⁹) = 0.1 m.
Problem 4
Answer and explanation
1.989e-19 J
E = h f = (6.63 × 10⁻³⁴) × (3 × 10¹⁴) = 1.989 × 10⁻¹⁹ J.
Problem 5
Answer and explanation
The photoelectric effect is light knocking electrons out of a metal surface. It only works when the light's frequency is high enough, no matter how bright a lower-frequency light is. This shows light delivers energy in discrete packets (photons) whose energy depends on frequency (E = h f) — evidence for light's particle nature.
Problem 6
Answer and explanation
750000000000000 Hz
f = c ÷ λ = (3 × 10⁸) ÷ (4 × 10⁻⁷) = 0.75 × 10¹⁵ = 7.5 × 10¹⁴ Hz.