The electromagnetic spectrum and its uses

Answer Key - Grade 11 Science Worksheet

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

1. 1.

   A germicidal lamp gives off 254 nm photons. With hc = 1,240 eV·nm, what is each photon's energy in eV, Ari?

   4.88 eV
2. 2.

   A red LED gives off 620 nm photons. With hc = 1,240 eV·nm, what is each photon's energy in eV, Bo?

   2 eV
3. 3.

   A lab X-ray source gives off 0.124 nm photons. With hc = 1,240 eV·nm, what is each photon's energy in eV, Esme?

   10,000 eV
5. 4.

   Using the device table, which wave has the longest wavelength, and about how long is it, Jun?

   • Microwave oven, about 12 cm, since GHz is the biggest unit
   • FM radio, about 3.1 km
   • FM radio, about 3.1 m
   • FM radio, about 0.33 m
6. 5.

   Using the device table, which wave has the highest photon energy, and why, Kira?

   Use the picture in question 4.

   • FM radio, since the longest waves carry the most energy
   • The germicidal lamp: 254 nm is the shortest wavelength
   • The TV remote, since 940 is the biggest number
   • The microwave oven, since 2.45 GHz is a big number
7. 6.

   A building is 20 m wide. Using the device table, which wave bends (diffracts) most around it, Luz?

   Use the picture in question 4.

   • FM radio: its 3 m wavelength is closest to the building's size
   • The TV remote, since infrared goes around corners
   • The germicidal lamp, since higher-energy waves bend more
   • Wi-Fi, since it passes through walls instead of bending
8. 7.

   A microwave oven runs at 2.45 GHz. What are its wavelength and the spacing of hot spots (half a wavelength), Milo?

   • Wavelength 12.2 cm; hot spots about 6.1 cm apart
   • Wavelength 12.2 m; hot spots about 6.1 m apart
   • Wavelength 6.1 cm; hot spots 3.1 cm apart
   • Wavelength 12.2 cm; hot spots 12.2 cm apart, one wavelength
9. 8.

   Water absorbs 4.19 J per gram per °C. An oven puts 700 W into 250 g of water for 60 s. What is the temperature rise, Pia?

   • About 80 °C, doubling the power
   • About 0.67 °C, leaving out the time
   • About 40 °C
   • About 40,000 °C, using 0.25 kg with joules per gram
10. 9.

    Ren compares two 1.0 m telescopes: one sees 500 nm light, one sees 21 cm radio waves. Which resolves finer detail, and by what factor?

    • The optical one, about 420,000 times finer
    • The optical one, about 42 times finer
    • Neither: both have a 1.0 m diameter
    • The radio one, since longer waves reach farther
11. 10.

    The James Webb telescope observes infrared. Why does that help it see the most distant galaxies, Zee?

    • Infrared is the one kind of light that crosses space
    • Infrared photons carry more energy, so they travel farther
    • Distant galaxies give off infrared light and nothing else
    • Cosmic expansion stretches their light into the infrared