The electromagnetic spectrumIB MYP Physics: Mind map

Exam questions on The electromagnetic spectrum

1. A smartphone uses several parts of the electromagnetic spectrum. It uses radio waves for mobile calls, microwaves for Wi-Fi, infrared for face recognition and visible light from its screen.
   Radio waves have a longer wavelength than visible light. State how the frequency of radio waves compares with that of visible light and explain why.2 marks
2. A local radio station broadcasts at a frequency of 100 MHz (1.0 × 10⁸ Hz). A home Wi-Fi router uses microwaves with a frequency of 2.4 GHz (2.4 × 10⁹ Hz). All electromagnetic waves travel at 3.0 × 10⁸ m/s in air.
   Calculate the wavelength of the microwaves used by the Wi-Fi router.2 marks
3. A student tests how well different sunscreens block ultraviolet (UV) radiation. She uses special beads that change from white to purple when UV hits them, and scores the colour from 0 (white) to 5 (darkest purple). Each sample of beads is covered with clear plastic film. She spreads a thin layer of sunscreen on the film, then shines the same UV lamp on the sample for 10 minutes. The film with no sunscreen gives a score of 5. The film with SPF 15 sunscreen gives 3, SPF 30 gives 2 and SPF 50 gives 1.
   State a hypothesis for this investigation, with a scientific reason, and identify one control variable.3 marks