Observing with Light Waves

Question 1

Which of the following lists correctly matches four parts of the electromagnetic spectrum with an astronomical object or phenomenon that is best observed at that wavelength?

Accepted Answer

Radio – cold hydrogen gas clouds; Infrared – dusty star‑forming regions; Visible – galaxies and nebulae; X‑ray – black‑hole jets

Answer

Radio – black‑hole jets; Infrared – cosmic microwave background; Visible – hot young stars; X‑ray – cold hydrogen gas clouds

Answer

Radio – pulsars; Infrared – galaxies; Visible – cosmic microwave background; X‑ray – dust clouds

Answer

Radio – cold hydrogen gas clouds; Infrared – dusty star‑forming regions; Visible – planets; Ultraviolet – black‑hole jets

Question 2

Dr. Rivera wants to observe the X‑ray glow from a newly discovered neutron star. She can either (1) place an X‑ray detector on a high mountain in the Andes, or (2) launch a small X‑ray telescope into orbit. Which statement correctly explains why the space‑based option is necessary for her study?

Accepted Answer

The Earth's atmosphere absorbs almost all X‑rays, so even at high altitude very few reach the ground, making a ground detector ineffective.

Answer

The atmosphere bends X‑rays away from the surface, so they never travel straight down to a detector.

Answer

Only gamma‑rays are blocked by the atmosphere; X‑rays pass through freely, so a mountain‑top instrument would work as well as a space telescope.

Answer

Mountaintop sites are so cold that X‑ray detectors cannot produce a usable signal.

Question 3

Which statement best explains why the Hubble Space Telescope mainly observes visible light while the James Webb Space Telescope mainly observes infrared light?

Accepted Answer

Hubble looks at visible light because most stars and galaxies shine brightest there and its mirrors are optimized for that range; JWST looks at infrared because very distant galaxies are red‑shifted into infrared and because infrared can penetrate dust clouds that hide objects in visible light.

Answer

Hubble observes visible light because Earth’s atmosphere blocks it, so the telescope must be in space; JWST observes infrared because infrared easily passes through the atmosphere and can stay on the ground.

Answer

Hubble uses visible light because infrared detectors had not been invented when it was built; JWST uses infrared to study the surface of the Sun.

Answer

Hubble uses visible light to see planets in detail; JWST uses infrared because infrared telescopes must be placed on the Moon.

Try three questions

Which of the following lists correctly matches four parts of the electromagnetic spectrum with an astronomical object or phenomenon that is best observed at that wavelength?

Which statement best explains why the Hubble Space Telescope mainly observes visible light while the James Webb Space Telescope mainly observes infrared light?

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