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PHYS 284 - INTRO TO ASTRONOMY > Lesson 5 > Flashcards

Lesson 5 Flashcards

1
Q

Why is light a form of energy? What type of energy is it?

A

Light is a form of energy because it has warmth

- the energy that light carries is radiative energy

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2
Q

What are scientists more interested when it comes to measuring the energy of light?

A

They are interested in the rate that light transfers energy rather than the total energy it carries

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3
Q

What is power? What is the unit measured?

A

Power is the rate of energy flow

- it is measured in watts

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4
Q

What does white light consist of?

A

White light is made up of all the other colours (sunlight is white light)

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5
Q

What does the colour black signify?

A

Black is the absence of light or colour

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6
Q

What four things can matter do to light when it interacts with it?

A
  1. emission - comes from a matter emitting radiative energy or a light emitting radiative energy
  2. absorbtion - absorbed energy from light causes skin to warm
  3. transmission - re-emission of energy
  4. reflection - light bounces a) in the same direction or b) scattered
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7
Q

What are the three properties of a wave?

A
  1. it has a wavelength (the distance between two peaks)
  2. it has frequency (the number of times per second a wave goes up and down)
  3. speed (how fast the peaks travel)
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8
Q

What is a particle?

A

A rigid body of mass

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9
Q

What is a wave?

A

A repetitive motion of non-solid substances (water or air)

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10
Q

How are light and gravity analogous?

A

Because the are both energy emitted from a source

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11
Q

What is the emission source of gravity?

A

Matter

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12
Q

What is the emission source of light?

A

Charge

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13
Q

What is a photon?

A

A particle of light

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14
Q

When do electrons move?

A

When light passes by - light carries a vibrating electric field

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15
Q

How fast do electromagnetic waves travel?

A

At the speed of light

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16
Q

What is the formula for the speed of light?

A

speed of light (c) = wavelength x frequency

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17
Q

What does a longer wavelength mean?

A

A lower frequency

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18
Q

What does a shorter wavelength mean?

A

A higher frequency

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19
Q

What is Planck’s constant? What is it measured in?

A

It measures the energy of light

- It is the units of joules per second

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20
Q

What is the highest frequency found in nature? What part of the spectrum does this frequency belong to?

A

The highest frequency is a zetahertz

- these are gamma rays

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21
Q

What is the range of frequencies visible to humans?

A

400nm (blue) to 700nm (red)

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22
Q

What is the order of frequencies in the light spectrum, going from the highest frequency to the lowest?

A

gamma rays - x-rays - UV - visible light - infrared - microwaves - radio waves

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23
Q

Who first proposed the idea of the atom?

A

Democratus

24
Q

What are atoms composed of?

A

Protons, neutrons, and electrons

25
Q

What two properties to particles have?

A

They contain both mass and charge

26
Q

What two units does charge come in?

A

Positive and Negative

27
Q

What are the two properties of charge?

A

Charges cannot be cut (ex. you cannot have 0.5 positive charge) and oppositely charged particles attract, while similarly charged particles repel

28
Q

What property does every atom of a given element have?

A

They all have the same number of protons, but the numbers of their electrons can vary

29
Q

How do atoms and molecules interact with each other?

A

Through strong and weak forces

30
Q

What three phases of can matter take on?

A
  1. solid phase: atoms are rigidly locked together by mutual forces
  2. liquid phase: atoms experience a net force with spring-like characteristics
  3. gas phase: atoms are free to move around as if free from any net force
31
Q

What is an atomic number?

A

the number of protons in a nucleus

32
Q

What is an atomic mass number?

A

the number of protons and neutrons in an atom

33
Q

What is a molecule?

A

Two or more atoms

34
Q

What is an isotope?

A

The same number of protons but a different number of neutrons

35
Q

What is sublimation?

A

Vaporization from a solid

36
Q

What is evaporation?

A

Vaporization from a liquid

37
Q

What is molecular dissociation?

A

When collisions become so violent in the atom (at high temperatures) that the chemical bonds that hold them together are broken

38
Q

What is ionization?

A

The process of stripping electrons from atoms

39
Q

Why do phases of the same material (ex. hydrogen) behave differently?

A

Because of the difference in their chemical bonds

40
Q

What is plasma?

A

It is a type of hot gas in which atoms have become ionized

41
Q

What are the two factors for determining what phase a substance takes?

A

Temperature and pressure

42
Q

What is pressure?

A

the force per unit area pushing on an object’s surface

43
Q

What is spectroscopy?

A

The process of obtaining and reading a spectrum

44
Q

What are the three basic types of spectra?

A
  1. continuous spectrum - the spectrum that spans all possible wavelengths without interruption
  2. emission spectrum - a thin or low-density cloud of gas emits light only at specific wavelengths that depend on its composition; it produces a spectrum with bright emission lines
  3. absorption spectrum - a cloud of gas between us and a lightbulb can absorb light of specific wavelengths, leaving dark absorption lines in the spectrum
45
Q

What is a chemical fingerprint?

A

the spectrum of light produced by a material (due to its specific properties)

46
Q

What is a blackbody?

A

An object that can absorb light but from which light cannot easily escape

47
Q

What does a blackbody’s thermal radiation depend on?

A

Only on temperature

48
Q

What are the properties of dense objects like stars?

A

They all behave as blackbodies

49
Q

What happens when a blackbody heats up?

A

there is an increased accumulation of photons, so it radiates energy as thermal radiation (blackbody radiation) and it changes colour (from red to white hot)

50
Q

What do the laws of blackbody radiation describe?

A

How light changes with colour

51
Q

What are the two laws of blackbody radiation?

A
  1. hotter objects emit more radiation per unit surface area at every wavelength
  2. hotter objects emit more of their light at shorter wavelengths (high energy)
52
Q

What is the doppler effect?

A

The observation that an object’s pitch (in the auditory modality) changes as a function of its distance from us

53
Q

Does the doppler effect exist in the frequency of light? How is it measured?

A

Yes

- it is measured from shifts in the wavelengths of spectral lines

54
Q

What wavelength does an object moving towards us have?

A

A blue shift (a shift to blue from the lab)

55
Q

What wavelength does an object moving away from us have?

A

A red shift (a shift to red from lab)

56
Q

What is the only information a doppler effect can give us?

A

The speed at which an object is moving towards us or away from us (not anything other than towards or away)

PHYS 284 - INTRO TO ASTRONOMY (28 decks)

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