Observing with Light Waves

Science · Space Exploration · ages 11-13

Name ______________________ Date ____________

On a clear mountain, a visible-light telescope receives starlight, but a direct X-ray telescope receives no astronomical X-rays. What explains this?
- X-rays run out of energy because they travel much farther than visible light
- Air transmits visible light but absorbs the incoming astronomical X-rays
- Mountain rocks turn all incoming astronomical X-rays into visible light
Which listed region of the electromagnetic spectrum has the shortest wavelengths?
- Gamma rays
- Radio waves
- Visible light
Hubble can observe ultraviolet, visible and some near-infrared light.
Circle one: True False
Some light from a very distant galaxy was emitted as visible light. It reaches us in Webb's infrared range. What explains this change?
- Expansion stretches the travelling light to longer wavelengths
- Long travel time gradually slows the light down to an infrared speed
- Dust filters out blue light and stretches the surviving waves into infrared
Scientists add a map of extremely hot gas near a galaxy's black hole to its visible-light image. Which telescope makes the hot-gas map described in the lesson?
- A radio telescope made to map cold interstellar gas
- An infrared telescope made to map warm interstellar dust
- An X-ray telescope made to map extremely hot gas
Astronomers want to map cold gas clouds where stars may form. Which telescope matches the radiation described for these clouds in the lesson?
- An X-ray telescope, because all gas emits mostly X-rays
- A radio telescope, which detects radiation from cold gas
- A gamma-ray telescope, because every cold cloud produces gamma rays
Scientists want to detect gamma rays arriving from space themselves, rather than secondary signals made in Earth's air. Which plan does this?
- In space, where incoming gamma rays reach the detector directly
- On a mountain, by measuring secondary flashes made in Earth's air
- Underwater, after gamma rays have crossed the whole atmosphere
Mia says microwaves are used only for cooking, never for astronomy. Which observation from the lesson provides a microwave counterexample to her claim?
- Measuring radiation from warm dust around newly forming stars
- Measuring radiation from extremely hot gas close to a black hole
- Measuring radiation from the cosmic microwave background

Answer key

For grown-ups. Fold this page away before handing over the rest.

Observing with Light Waves W1-mt_rbY77m8_s1-s1

Air transmits visible light but absorbs the incoming astronomical X-rays · Visible starlight can pass through clear air. Incoming astronomical X-rays are absorbed before reaching the mountain.
Gamma rays · Gamma rays have shorter wavelengths than visible light and radio waves.
True · Hubble's instruments cover ultraviolet, visible and part of the near-infrared region.
Expansion stretches the travelling light to longer wavelengths · Expansion stretches light to longer wavelengths. Infrared is not a slower speed of light, and filtering out blue light does not stretch the surviving waves.
An X-ray telescope made to map extremely hot gas · X-rays reveal extremely hot gas, including gas near black holes. Other wavelengths give different information about the galaxy.
A radio telescope, which detects radiation from cold gas · Radio observations can map radiation from cold gas clouds. The gas need not be extremely hot to produce a useful radio signal.
In space, where incoming gamma rays reach the detector directly · A space detector can receive incoming gamma rays directly. Ground observatories instead measure secondary signals produced by interactions in the air.
Measuring radiation from the cosmic microwave background · The cosmic microwave background is measured at microwave wavelengths. The lesson's warm-dust example uses infrared, and its extremely hot gas example uses X-rays.