The electromagnetic spectrum and its uses

Answer Key - Grade 11 Science Worksheet - Challenge Me

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

1. 1.

   A probe at the Sun–Earth L1 point is 1500000 km away. Bo sends a command and gets the reply. How long is the round trip?

   10.01 s
2. 2.

   A satellite hovers 35786 km up. Esme sends a question up and down to a friend, and the reply goes up and down. How long is the delay?

   0.48 s
3. 3.

   A 5G phone gets strong 28 GHz signals outdoors but weak ones indoors; lower-frequency signals reach indoors better. Which explains this, Kira?

   • Higher-frequency photons carry less energy, so they stop
   • Higher-frequency waves travel slower, so they arrive late
   • Shorter 28 GHz waves are blocked more by walls
   • Walls absorb low frequencies more than high ones
4. 4.

   Luz builds a half-wave antenna for a 98.1 MHz FM station. About how long should it be?

   • About 15 cm, a tenth of a wavelength
   • About 3.1 m, one whole wavelength
   • About 0.76 m, a quarter wavelength
   • About 1.5 m
5. 5.

   Milo says microwaves cook food from the inside out. Water absorbs 2.45 GHz waves within a centimeter or two. Judge the claim.

   • Supported: the middle absorbs more because it is deeper
   • Supported: microwaves pass through the surface and heat the middle
   • Not supported: the surface absorbs first; heat then conducts inward
   • Not supported: microwaves heat the surface of the food
6. 6.

   Noah says the sky is blue because the air absorbs blue light. Air scatters light roughly as 1/λ⁴. Judge the claim.

   • Not supported: air scatters blue about 4 times more than red
   • Not supported: air scatters red light more than it scatters blue
   • Supported: scattering and absorbing are one and the same process
   • Supported: the blue light we see is what the air lets through
7. 7.

   Pia wants to test whether a wall weakens a Wi-Fi signal. Which design is best?

   • Measure with the wall in place, then again much farther from the router
   • Measure the router's label power and compare it with the wall's thickness
   • Measure once in each room, wherever the signal is easiest to reach
   • Measure at the same distance with and without the wall, several times each
8. 8.

   Why do X-ray telescopes orbit above the atmosphere, while many radio telescopes work on the ground, Ren?

   • Radio waves travel faster, so they reach the ground
   • Radio waves carry more energy, so they pass through air
   • Air absorbs X-rays but passes many radio waves
   • X-rays are too bright to be measured from the ground
9. 9.

   A thermal camera shows a warm mug in bright yellow and a cold table in blue. What do the colors tell Tala?

   • The camera sees the visible colors of each object
   • The colors show how fast the objects are moving
   • The software assigns colors to the infrared intensity
   • The mug gives off yellow light and the table gives off blue light
10. 10.

    Zee tunes a radio telescope to the 1,420 MHz hydrogen line. What wavelength is that, and why can radio cross dust that blocks light?

    • About 21 m; dust grains are far smaller than that wavelength
    • About 2.1 cm; dust grains are larger than the wavelength
    • About 21 cm; dust grains are far smaller than that wavelength
    • About 21 cm; radio waves carry more energy, so they push through