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ASTR 209 Midterm Exam 2026/2027 |
Comprehensive Practice Q&A Review |
Astronomy 209 Course Study Pack | Grade A
Prep
How do we see thing?
✓ Answer: Some object emits light, some reflect light from another object, and modifying
it
How do we know light is a wave?
There is a pattern of rings that form after light from a laser passes through a small circular hole
(diffraction pattern)
Waves have a the ability to bend around corners
Is the speed of a wave constant or variable?
Constant (~300 thousand km/s)
What type of wave is a light?
Electromagnetic wave
What is the parcel of energy that is carried by light called?
A photon
What determines the wavelength and frequency of a light wave?
The vibrations of the electric field
What do we perceive wavelength of light as?
Colour
What wavelengths is the human eye sensitive to?
Wavelengths ranging from ~400-800nm (visible light)
How is frequency calculated? What are the units?
speed of light (m/s)/wavelength (m)
Units = cycles/s or Hz
What does a longer wavelength mean? Shorter wavelength?
Longer = lower frequency
Shorter = higher frequency
, What is the electromagnetic spectrum? (from largest to smallest wavelength)
Largest:
Radio waves (wavelength longer than 1 mm)
Microwaves
Infrared waves (800 nm to 1 mm)
Visible light (400 nm to 800 nm)
Ultraviolet (10 nm to 400 nm)
X-ray (0.1 nm to 10 nm)
Gamma ray (less than 0.1 nm)
Smallest:
Do we get any information from the speed of a wave?
In astronomy, there is almost never useful information in the speed of the electromagnetic waves
that we observe (because waves travel at the same speed) - only in special situations we can
detect that waves travel at different speeds through space
What does the lens in the eye do?
Focus light on the fovea
What does a small pinhole aperture do? Large pinhole?
Small - image sharper but darker
Large - image brighter but blurry
What is the function of the lens of a telescope?
Makes the aperture (pinhole) as large as possible so that it...
- Collect more light
- Make the image brighter
- See faint stars that would otherwise be invisible
Why are mirrors used in the largest telescopes?
You only need to polish one surface of a mirror (lens would need to have both sides polished)
You can support the mirror on the back side to keep it in place (can on support a lens around the
edges)
What are telescopes with a concave mirror in the aperture called? Lens?
Mirror - reflectors
Lens - refactors
What are the aspects of angular resolution/separation?
The same object at a larger distance appears smaller (same object at a smaller distance has a
larger angular size)
Light rays from car headlights are nearly parallel when the car is farther away but make a larger
angle when he car is closer
ASTR 209 Midterm Exam 2026/2027 |
Comprehensive Practice Q&A Review |
Astronomy 209 Course Study Pack | Grade A
Prep
How do we see thing?
✓ Answer: Some object emits light, some reflect light from another object, and modifying
it
How do we know light is a wave?
There is a pattern of rings that form after light from a laser passes through a small circular hole
(diffraction pattern)
Waves have a the ability to bend around corners
Is the speed of a wave constant or variable?
Constant (~300 thousand km/s)
What type of wave is a light?
Electromagnetic wave
What is the parcel of energy that is carried by light called?
A photon
What determines the wavelength and frequency of a light wave?
The vibrations of the electric field
What do we perceive wavelength of light as?
Colour
What wavelengths is the human eye sensitive to?
Wavelengths ranging from ~400-800nm (visible light)
How is frequency calculated? What are the units?
speed of light (m/s)/wavelength (m)
Units = cycles/s or Hz
What does a longer wavelength mean? Shorter wavelength?
Longer = lower frequency
Shorter = higher frequency
, What is the electromagnetic spectrum? (from largest to smallest wavelength)
Largest:
Radio waves (wavelength longer than 1 mm)
Microwaves
Infrared waves (800 nm to 1 mm)
Visible light (400 nm to 800 nm)
Ultraviolet (10 nm to 400 nm)
X-ray (0.1 nm to 10 nm)
Gamma ray (less than 0.1 nm)
Smallest:
Do we get any information from the speed of a wave?
In astronomy, there is almost never useful information in the speed of the electromagnetic waves
that we observe (because waves travel at the same speed) - only in special situations we can
detect that waves travel at different speeds through space
What does the lens in the eye do?
Focus light on the fovea
What does a small pinhole aperture do? Large pinhole?
Small - image sharper but darker
Large - image brighter but blurry
What is the function of the lens of a telescope?
Makes the aperture (pinhole) as large as possible so that it...
- Collect more light
- Make the image brighter
- See faint stars that would otherwise be invisible
Why are mirrors used in the largest telescopes?
You only need to polish one surface of a mirror (lens would need to have both sides polished)
You can support the mirror on the back side to keep it in place (can on support a lens around the
edges)
What are telescopes with a concave mirror in the aperture called? Lens?
Mirror - reflectors
Lens - refactors
What are the aspects of angular resolution/separation?
The same object at a larger distance appears smaller (same object at a smaller distance has a
larger angular size)
Light rays from car headlights are nearly parallel when the car is farther away but make a larger
angle when he car is closer
