The electromagnetic spectrum and its uses

Answer Key - Grade 11 Science Worksheet - Building Confidence

Circle the best answer, or write your answer on the line.

1. 1.

   Ari tunes a radio to 100 MHz. What is the wavelength of the signal?

   3 m
2. 2.

   Bo's phone uses a signal at 1.5 GHz. What is the wavelength of the signal?

   0.2 m
3. 3.

   Esme listens to an AM station at 600 kHz. What is the wavelength of the signal?

   500 m
4. 4.

   Which list orders these waves from lowest to highest photon energy: UV, radio, X-rays, infrared, visible, Jun?

   • Radio, infrared, visible, UV, X-rays
   • Infrared, radio, visible, X-rays, UV
   • X-rays, UV, visible, infrared, radio
   • Radio, visible, infrared, UV, X-rays
5. 5.

   Green light is 550 nm and red light is 700 nm. Which has the higher frequency, and about what is it, Kira?

   • Red, about 4.3 × 10¹⁴ Hz, since longer waves have higher frequency
   • Both the same, since light has one speed
   • Green, about 5.5 × 10¹⁴ Hz
   • Green, about 5.5 × 10¹¹ Hz
6. 6.

   Why can ultraviolet sunburn skin when visible light of the same brightness does not, Noah?

   • UV travels faster than visible light, so it hits harder
   • UV is a hotter kind of light than visible light is
   • UV has longer wavelengths, so each photon carries more energy
   • Each UV photon carries more energy, enough to damage skin cells
7. 7.

   Why can Wi-Fi pass through a wall, but a TV remote's infrared cannot, Pia?

   • Radio waves travel faster than infrared, so they get through
   • Infrared is too bright to pass through a wall
   • Walls let 12 cm radio waves through but block infrared
   • Wi-Fi has more energy per photon than infrared
8. 8.

   A radio signal and a flash of light leave the Moon together, 384,400 km away. Which arrives first, Ren?

   • They arrive together, after about 1.3 minutes
   • They arrive together, after about 1.3 s
   • The light, since its frequency is higher
   • The radio signal, since its wavelength is longer
9. 9.

   In a vacuum, a wave's frequency doubles. What happens to its wavelength, Tala?

   • It halves, because the speed stays fixed
   • It doubles, because the wave speeds up
   • It stays the same, because it is the same kind of wave
   • It quadruples, because λ goes as f²
10. 10.

    Wi-Fi works at 2.4 GHz and at 5 GHz. Which has the longer wavelength, and by about how much, Zee?

    • 2.4 GHz, by a factor of about 2.4
    • Neither: they both travel at c
    • 5 GHz, by a factor of about 2
    • 2.4 GHz, by a factor of about 2