ASTRO 1500 Trivia - Feb 7th

In Astronomy, luminosity is measured in a unit called a

• Newton/second

• curie/lightyear

• Erg/second

• Joule

Answer explanation

In astronomy, the unit of luminosity is erg/sec

You are staring at the Sun (Ouch). If you double the distance between you and Sun (get farther out), how will the luminosity of the Sun change?

• It will get 4 times dimmer

• It won't change

• It will get 2 times dimmer

• It will get 4 times brighter

Answer explanation

The luminosity is an intrinsic property of the star. In other words, how you look at the star makes no difference, the luminosity will always be the same.

You are still staring at the Sun for some reason. If you again double the distance between you and Sun, how will the brightness of the Sun change?

• 2 times dimmer

• 4 times brighter

• 4 times dimmer

• It will stay the same

Answer explanation

Because the brightness goes down with an inverse square law, the Sun will appear 4 times dimmer. It will still probably burn your eyes though.

The peak of the sun's spectrum appears to us as ...

• UV rays

• X-rays

• Radio Waves

• Visible light

Answer explanation

This is why we evolved to see this type of light, it's the brightest and most abundant

A human being radiates most of their light in the __ part of the spectrum.

• UV

• Visible

• IR

• Gamma Rays (I am the hulk)

Answer explanation

Body temperature is between 10 and 10^3 (1000) degrees K, so humans radiate the the IR section of the EM spectrum. (This is how night vision works)

Which is hotter?

• Blue Star

• Red Star

• We can't tell with this information

Answer explanation

See Wien's law, an increase in temperature will lead to a decrease in wavelength, meaning an increase in frequency, which means bluer light.

Which of these is more luminous?

• Blue Star

• Red Star

• We can't know with this information

Answer explanation

The luminosity equation depends on both the radius of the star and it's temperature. A big red star could be more luminous than a small blue star. We need to know more about the sizes.

How long is the wavelength of microwaves?

• 1 mm - 30 cm

• 750 nm - 1 mm

• 400nm - 700 nm

• 1.24 meters

Answer explanation

A household microwave has produces light with a wavelength of 12.2 cm, which is why a grape will catch fire in a microwave!

True or False: A bound electron can only orbit at certain energy levels and cannot occupy areas in-between these levels.

• True

• False

Answer explanation

True, an due to quantum mechanics an electron cannot occupy the space between orbits

When we look at a radiating blackbody, we see it as the color ...

• Blue

• Red

• Black

• Depends on the temperature

Answer explanation

According to Wien's law, the color of light emitted by a blackbody is entirely dependent on the temperature.