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SingaporePhysicsQuick questions
Waves, Light and Sound
Quick questions on The electromagnetic spectrum and sound explained: O-Level Physics
6short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is the electromagnetic spectrum?Show answer
The electromagnetic (EM) spectrum is the family of transverse waves that all travel at the same speed in a vacuum, the speed of light, . They differ in frequency and wavelength. In order of increasing frequency (and decreasing wavelength):
What are dangers of high-frequency EM waves?Show answer
The higher-frequency waves carry more energy and can damage cells. Ultraviolet can cause skin cancer and eye damage; X-rays and gamma rays can damage or kill living cells, which is why exposure is carefully limited.
What are sound waves?Show answer
Sound is a longitudinal wave produced by a vibrating object (such as a loudspeaker cone or vocal cords). The vibrations push and pull the surrounding particles, creating compressions and rarefactions that travel outward. Because it needs particles to pass on the vibration, sound cannot travel through a vacuum.
What is q1?Show answer
List the electromagnetic spectrum in order of increasing frequency. [2 marks]
What is q2?Show answer
State one use of infrared radiation and one danger of X-rays. [2 marks]
What is q3?Show answer
Explain why an astronaut on the airless Moon cannot hear a sound but can see a flash. [2 marks]
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