Class Notes (1,100,000)
CA (630,000)
WLU (20,000)
AS (200)
AS101 (200)
Lecture 12

AS101 Lecture Notes - Lecture 12: Reflecting Telescope, Refraction, Primary Mirror

Course Code
Patrick Mc Graw

This preview shows half of the first page. to view the full 2 pages of the document.
Astronomy Lecture 11
Why do we bother with telescopes?
- What things did Galileo observe when he pointed his telescope upwards
- Venus rotates just the moon, and that Venus is the brightest planet.
What make a good telescope?
- Magnification
- Size of optical components
- An astronomer with 20/20 vision
- Location
Refraction: the bending of light
- Refraction is the behind of a ray of light when it passes through into a new medium
- Light can change direction when interacting with matter
- Prism- white light comes in and it spreads out, light is bending. Short wavelength light bends
more than the long wavelength
- Observation of prisms show refraction depends on the wavelength of light; shorter wavelengths
bend more
- Newton’s idea
- A ray of light will reflect from a smooth surface at the same angle that it is incident with
- Special property: for parabolic mirrors, rays of light that are parallel converge at the same point
Refracting Telescope
- A primary or objective lens bends light and brings it to a focus
o The lens must be flawless throughout
- Different wavelengths of light are focussed at different locations :chromatic aberration
Reflecting telescope
- Light bounces from an convex (inwardly curved) primary mirror
- A smaller secondary mirror can be used to redirect the light
Telescopes are light buckets
- If you want to get more light, you need to emit more light
- A larger mirror will produce a brighter image
- Light Gathering power (LGP)- is proportional to the area of the primary mirror or lens
o A two metre mirror has four times the LGP
You're Reading a Preview

Unlock to view full version