Quiz 2 Review

Question 1

Why couldn’t Galileo successfully measure the speed of light?

Answer 1

attempt: light was too fast to measure

Question 2

How did Ole Roemer determine speed of light

Answer 2

Measured speed of light by observing eclipses of Jupiter’s moons

Question 3

What is the speed of light? About how far does light travel in one nanosecond?

Answer 3

• light has a finite speed
• takes time for light to travel across the universe
• Lightspeed is the fastest speed the universe will allow
• Matter cannot travel at the speed light; it always go slower
• 1 Nano second equals 1 billionth of a second (186,282 measures in vacuum)

Question 4

What is a light year? What does it measure?

Answer 4

Light year: The distance beam of light travels in one year (5.9 trillion years)

distance = speed x time (182,282 miles per second)

Question 5

What is it about light and the universe that allows astronomers to be able to look back into the past?

Answer 5

Telescopes are like time machines
-by looking across the universe we are looking into the past and can watch universe expand
- see objects not as how they are now but as they were at the time when they released the light that had traveled across the universe

Question 6

What is interference?

Answer 6

When two or more waves of same wavelength and frequency join each other to form a single wave; causes interference 

constructive interference: Makes bigger waves

destructive interference: cancels each other out when waves mix

Question 7

What is wavelength and frequency?

Answer 7

Wavelength: is the distance between two wave crest and it will be the same for troughs

Frequency:  The number of vibrations that passes over a given spot in one second and it is measured and cycles per second (hz)

Question 8

What is electromagnetic radiation?

Answer 8

Is a form of energy that includes radio waves, microwaves, x-rays, and gamma rays; As well as visible light

Question 9

What are photons?

Answer 9

Fundamental subatomic particles that carry electromagnetic force (light particles)

Question 10

What is the relationship between wavelength, frequency, and energy for light?

Answer 10

shorter wavelength and higher frequency = greater energy

longer wavelengths and lower frequency = lower energy

Question 11

Which type of light has the highest energy? The lowest energy?

Answer 11

Radio waves - Longest wavelength; lowest energy light
Microwave -
Infrared - longer wavelength lower energy than visible light
Visible light-
Ultraviolet - Shorter wavelength; higher energy
X-ray - High frequency 
Gamma Ray - shortest wavelength ; highest energy light

Question 12

Which type of light travels fastest?

Answer 12

All types of light travel at the same speed

Question 13

What is blackbody radiation? How is it useful to astronomers?

Answer 13

1. Absorbs ALL light that falls upon it
2. Emits light ONLY as a result of its temperature

Question 14

How does the way a stove burner (or any hot glowing object) change the way it emits as its temperature gets hotter and hotter?

Answer 14

Every object emits light energy over a wide range of wavelengths; Infrared is what we feel as heat

Behave like black bodies
- light we see is because of temperature
- growing because of their temperature
Means we can measure temperature

Question 15

How does an object’s blackbody curve change as its temperature changes? What does the peak of the curve tell us about the temperature of the object?

Answer 15

As an object gets hotter it radiates more light and with a peak that moves toward shorter wavelengths

• wavelength and temperature are inversely related

LOW TEMPERATURE glows with light that has the peak of black body curve at LONG WAVELENGTH

HIGH TEMPERATURE glows with light that has the peak of black body curve at SHORT WAVELENGTH

Question 16

Color are the hottest stars? What color are the coolest stars?

Answer 16

Hottest stars = glow light blue or dark blue (very hottest)

Cooler stars = glow red or orange or yellow (change color as surface temperature rises)

Question 17

What color is the sun? What color marks the peak of its blackbody curve?

Answer 17

It is WHITE due to the mix of colors ; peak of black body curve is green

Question 18

What’s the three types of spectra?

Answer 18

Continuous spectrum, Absorption-line spectrum, and Emission-line spectrum

Question 19

Continuous spectrum

Answer 19

a full rainbow of colors
- black body curve (basically);
- produced by a hot glowing solid, liquid, or dense gas
EX: incandescent light bulb, molten lava, stove burners, sun

Question 20

Absorption spectrum

Answer 20

a full rainbow of colors with lines of colors missing
- created as light from a hot glowing object passed through a cool transparent gas
- gas or atmosphere absorbing some of the color (black line in spectrum)

Question 21

Emission spectrum

Answer 21

line spectrum
- individual lines of color
- produced by a hot glowing, Lowe density gas
( little bits of color instead of whole thing )