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How are wavelength, frequency, and energy related for photons of light?

Longer wavelength means lower frequency and lower energy.

From lowest energy to highest energy, which of the following correctly orders the different categories of electromagnetic radiation?

radio, infrared, visible light, ultraviolet, X rays, gamma rays

Which of the following statements about electrical charge is true?

A positive charge and a negative charge will attract each other.

Which of the following statements about electrons is not true?

Electrons orbit the nucleus rather like planets orbiting the Sun.

An atom of the element iron has an atomic number of 26 and an atomic mass number of 56. If it is neutral, how many protons, neutrons, and electrons does it have?

26 protons, 30 neutrons, 26 electrons

When an atom loses an electron, it becomes


An electron-volt is

an amount of energy much smaller than a joule.

Everything looks red through a red filter because

the filter transmits red light and absorbs other colors.

Without telescopes or other aid, we can look up and see the Moon in the night sky because it

reflects visible light.

Which of the following objects is not a close approximation of a thermal emitter?

hot, thin gas

A gas heated to millions of degrees would emit

mostly X rays.

From laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 121.6 nanometers (nm). The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 121.8 nm. What can we conclude?

The star is moving away from us.

If we observe one edge of a planet to be redshifted and the opposite edge to be blueshifted, what can we conclude about the planet?

The planet is rotating.

Suppose you see two stars: a blue star and a red star. Which of the following can you conclude about the two stars? Assume that no Doppler shifts are involved. (Hint: Think about the laws of thermal radiation.)

The blue star has a hotter surface temperature than the red star.

What is an artificial star?

a point of light in Earth's atmosphere created by a laser for the purpose of monitoring atmospheric fluctuations

Currently, the largest optical telescope mirrors have a diameter of about

10 m.

Which of the following is not a good reason to place observatories on remote mountain tops?

to be able to observe at radio wavelengths

Why do astronomers need different telescope designs to observe across the electromagnetic spectrum?

Photons of different energy behave differently and require different collection strategies.

Which of the following wavelength regions cannot be studied with telescopes on the ground?

A) radio waves
B) ultraviolet
C) x rays
both B and C

In what part of the electromagnetic spectrum do the biggest telescopes on Earth operate?


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