Astrophysics Flashcards
How do lenses work?
They refract light at a glass-air boundary
What is the power of a lens measured in?
Dioptres, D
How is the power of a lens calculated?
Power = 1/focal length (m)
Outline the steps of drawing a ray diagram.
- Draw the ray parallel to the principle axis
- Draw the refracted ray so it passes through principle focus
- Draw ray from top of object through the middle of the lens which is undeviated
- Where two rays meet, that is where image is
What is the lens formula?
1/f = 1/u + 1/v
What does u stand for in the lens formula?
object distance
What does v stand for in the lens formula?
image distance
How can magnification, M be calculated?
M = v/u
Does magnification, M have units?
No
What must be considered in producing a good-quality refracting telescope?
Lens quality, lens diameter, angular magnification
How can angular magnification be calculated?
M = B/a where B is the angle with the eyepiece and a is the angle with the objective lens
In what unit are B and a in?
Radians, small angles
How are focal lengths and magnification related?
M = fo / fe
Define intensity.
The power per square meter
What is the Doppler effect?
The change of wavelength and frequency of a wave as the source moves away from or towards the observer
