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Define wavelength of light waves.
The distance between adjacent peaks of the wave.
Define frequency of light waves.
The number of times that any piece of the rope moves up and down each second.
Define speed for light waves.
All light travels through empty space at the same speed (the speed of light). The speed of any wave is its wavelength times its frequency.
If light has a long wavelength, what can you say about its frequency? Explain.
The longer the wavelength, the lower the frequency, and visa versa.
List the different forms of light in order from lowest to highest energy. Is the order the same from lowest to highest frequency? From shortest to longest wavelength?
Radio, Microwaves, Infrared, Visible, Ultraviolet, X Rays, Gamma Rays. Yes, no. Lower energy waves will have lower frequencies, but the longest wavelength.
What are the four major ways in which light and matter can interact? Give an example from everyday life.
Matter can:
1) emit light: light bulbs emit visible light
2) absorb light: your hand can absorb light when putting it near a light bulb, warming your hand
3) transmit light: glass and air transmit light, allowing it to pass through
4) reflect (scatter) light: light can bounce off matter. reflection is is when it bounces off in the same general way, scattering is when it bounties off more randomly
1) emit light: light bulbs emit visible light
2) absorb light: your hand can absorb light when putting it near a light bulb, warming your hand
3) transmit light: glass and air transmit light, allowing it to pass through
4) reflect (scatter) light: light can bounce off matter. reflection is is when it bounces off in the same general way, scattering is when it bounties off more randomly
Describe the conditions that lead to each of the three basic types of spectra. Which type is the Sun's spectrum? Why?
Continuous spectrum: rainbow of color
Absorption line spectrum: if a cloud of gas lies between us and a light source, we will see most of the continuous spectrum expect for some dark lines over the background rainbow
Emission line spectrum: if a thin cloud of gas emits light only a specific wavelengths that depend on composition and temperature, bright emission lines will show up agains a black background.
The sun emits a continuous spectrum
Absorption line spectrum: if a cloud of gas lies between us and a light source, we will see most of the continuous spectrum expect for some dark lines over the background rainbow
Emission line spectrum: if a thin cloud of gas emits light only a specific wavelengths that depend on composition and temperature, bright emission lines will show up agains a black background.
The sun emits a continuous spectrum
Why do atoms emit or absorb light of specific wavelengths? How does this fact allow us to determine the chemical composition of a distant object?
They correspond to particular energy level transitions in atoms or molecules. Every kind of atom, ion, and molecule produces a unique set of spectral lines, so we can determine an object's composition by identifying these lines.
Describe the Doppler effect for light and what we can learn from it. What does it mean to say that radio waves are blue-shifted?
The Doppler effect tells us how fast an object is moving toward or away from us. If something is blue-shifted (shorter wavelengths), an object is moving towards us. If they are red-shifted (longer wavelengths), they will be moving away.
What are the two key properties of a telescope and why is each important?
1) Light collecting area: describes how much light a telescope can collect
2) Angular resolution: determines the amount of detail in telescopic images; it is better for larger telescopes
2) Angular resolution: determines the amount of detail in telescopic images; it is better for larger telescopes
Distinguish between refracting and reflecting telescopes.
-Refracting: operates similar to an eye, using transparent lenses to collect and focus light.
-Reflecting: uses a precisely curved primary mirror to gather light. This mirror reflects the gathered light to a secondary mirror that lies in front of it. The secondary mirror reflects the light to a focus point where the eye can observe it.
-Reflecting: uses a precisely curved primary mirror to gather light. This mirror reflects the gathered light to a secondary mirror that lies in front of it. The secondary mirror reflects the light to a focus point where the eye can observe it.
List 3 ways Earth's atmosphere can hinder astronomical observations.
1. clouds can block night observations (also can't see anything in the daytime).
2. our atmosphere scatters the bright lights of cities which creates light pollution which can obscure telescopes
3. the ever changing motion, or turbulence, of air in the atmosphere bends light in constantly shifting patterns.
4. our atmosphere prevents most forms of light from reaching the ground at all
2. our atmosphere scatters the bright lights of cities which creates light pollution which can obscure telescopes
3. the ever changing motion, or turbulence, of air in the atmosphere bends light in constantly shifting patterns.
4. our atmosphere prevents most forms of light from reaching the ground at all
Briefly describe how adaptive optics and interferometry can improve astronomical observations.
It overcomes the blurring effects of Earth's atmosphere by accounting for the turbulence that causes rays of light from a star to dance around as they reach a telescope. With adaptive optics, mirrors in the telescope will do an exact opposite dance, canceling out the distortions so we end up with a clear picture.
Why is a sunflower yellow?
It reflects yellow light.
Compared to red light, does blue light have lower or higher frequency and energy and shorter or longer wavelength?
Red light: lower frequency, lower energy, and longer wavelength.
Blue light: higher frequency, higher energy, and shorter wavelength.
Blue light: higher frequency, higher energy, and shorter wavelength.