Chapter 5 Flashcards
What are Wave Properties?
Wavelength, Frequency, Period, Amplitude, Speed (always constant)
What is a Wavelength?
Distance between successive peaks (or troughs) if we freeze the wave at one moment in time.
What is a Period?
A related idea is the amount of time it takes for the pattern to repeat if you stay in the same place.
What is the Frequency?
The number of times the wave pattern will repeat (per second) if you stay at a fixed place - or how many waves (cycles) pass by per second. (Hertz)
Period and Frequency relationship
Period = 1/Frequency
Speed = ?
Distance/Time
Wavelength/Period
Wavelength * Frequency
Speef of Light Equation
C = Wavelength * Frequency
C = ?
3.0 x 10^8 m/s = 3.0 x 10^5 km/s = 300,000 km/s
Wavelength Unit
m,nm,mm
Frequency Unit
Hertz = Hz = 1/s
Propagation of Light
Light spreads out as it goes away from its source (Energy decreasing)
Inverse Square Law
The amount of light recieved by any given patch on the sphere gets diluted by the square of the distance from the source
What is an Electromagnetic Wave?
The result is a wave of combined electric and magnetic fields.
What is Radiation?
refers to any physical process in which energy passes from one place, through some intervening region to another place.
What do we sometimes refer to light as?
Electromagnetic Radiation
What is the Electromagnetic Spectrum?
When we split light into its components (rainbow).
Different ranges of wavelengths on the electromagnetic spectrum (shortest to longest). Gamma, Ultra, X, Infrared, FM Radio, Microwave, AM Radio.
Gamma, X, Ultraviolet, Infrared, Microwave, FM, AM
What color has the longest wavelength?
Red
Energy Proportions
Higher Energy = Higher Frequency
What light only reaches through the atmosphere?
Visible and Radio
What objects emit radiation all the time?
All
When charged particles move what is emitted?
light
What does a higher temp mean?
more jostling and more light get emitted
All motion stops at what temp?
0 K
What is thermal radiation?
is emitted by an opaque object, it shows emitted light intensity as a function of wavelength.
What is determined only by temp?
The emitted spectrum
What is Wien’s Law?
The higher the temp, the shorter the wavelength of peak emission. The hotter the object the bluer it looks.
What is the wavelength peak?
It is the point of the wavelength at which the objects emit the most energy.
What is Stefan-Boltzmann Law?
Total (summed over all wavelengths) energy emitted is proportional to the 4th power of temp (note heigh of curves)
What is Flux?
Energy per second per unit area
What is a continuous spectrum?
When we pass a beam of white sunlight through a prism, we see a rainbow-colored band of light.
What is dispersion?
Violet light is bent more than red light, causing the different wavelengths of light to spread out.
What is due to atoms in a thin gas?
Emission and Absorption
What is Emission?
Mostly dark some color.
What is Absorption?
Mostly color some dark spots.
Why do electrons absorb energy?
By absorbing energy they can more to energy levels further from the nucleaus.
How do electrons absorb radiation?
To leaping up
How do electrons emit radiation?
By falling down
What is the Doppler effect?
The motion of a light source toward or away form us changes our perception of the wavelength of the waves reaching us.
Light approaching objects is what?
blueshifted (shorter wavelengths)
Light receding from objects is what?
redshifted (longer wavelengths)
Why does the sky look blue?
Blue wavelengths from the sun scatter across the sky and spread out till they eventually reach your eye.
