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CAIE IGCSE Physics Electromagnetic Wave Speed

Practise using the common vacuum speed of all electromagnetic waves and distinguish it from sound speed while comparing travel times and wavelengths.

Syllabus
2026–2028
Course
Physics 0625

Exam points

  • state that every EM region travels at 3.0 × 10⁸ m/s in vacuum and nearly so in air
  • reject claims that radio, infrared, visible, ultraviolet, X-rays or gamma have different vacuum speeds
  • contrast electromagnetic travel with sound or ultrasound at about 340 m/s in air

3.3.2—All EM waves travel at the same high question 1

[Maximum number: 1]

An eclipse of the Sun happens when the Moon comes between the Earth and the Sun.
Which statement is correct?

A

Infrared radiation from the Sun disappears before visible light and ultraviolet radiation.

B

Ultraviolet radiation from the Sun disappears before visible light and infrared radiation.

C

Visible light from the Sun disappears before ultraviolet radiation and infrared radiation.

D

Infrared radiation, ultraviolet radiation and visible light from the Sun all disappear at the same moment.

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