The electromagnetic spectrumIB MYP Sciences: Mind map

Exam questions on The electromagnetic spectrum

1. A science teacher in Mumbai draws the electromagnetic spectrum on the board and asks her class to compare radio waves, visible light and gamma rays. She reminds them that all electromagnetic waves are transverse and that sunlight reaches Earth across empty space.
   A radio station broadcasts at a frequency of 100 MHz. The speed of radio waves is 3 × 10⁸ m/s. Calculate the wavelength of the radio waves.2 marks
2. In a hospital in Lagos, a patient with a broken wrist has an X-ray. The radiographer stands behind a lead screen to operate the machine. Later the hospital uses gamma rays to sterilise surgical instruments before they are sealed in packets.
   Explain how gamma rays can be used to sterilise surgical instruments.2 marks
3. Students in Perth, Australia, investigate sun protection. They place identical UV-sensitive beads under clear plastic film coated with sun cream of SPF 15, SPF 30 or SPF 50, and under film with no cream. The beads change from white to purple in ultraviolet light. The students time how long the beads take to become fully purple in strong sunlight, and each test is done once. The times are 25 s with no cream, 95 s with SPF 15, 170 s with SPF 30 and 290 s with SPF 50.
   State a testable hypothesis for this investigation, with a scientific reason, and identify the independent variable.3 marks