Chapter 5 Flashcards
What is collecting power in a telescope
It is how big a telescope is and how much light it collects
What is focusing power in a telescope
It is how it uses its mirrors and lenses to bend the path of light and create images
What is resolving power in a telescope
It is how clear the image is and how many details show
How does the size of the telescope affect the image
The size is directly proportional to the light collected, more light collected means a brighter image is shown.
What two methods does focusing power use
Refraction and reflection
What is refraction
It is the bending of light due to it shifting between one medium to another and changing speed
What telescopes are called refractors
Ones that use lenses to collect and focus light
What are disadvantages of refractors
Large lenses are extremely expensive, a large lens is only supported in the middle and will sag, dispersion causes images to have colored fringes, many lens materials absorb short-wavelength light
What are reflecting telescopes
What astronomers mainly use today, are telescopes that use mirrors to focus the light
How do reflecting mirrors work
A secondary mirror may be used to deflect the light through a hole in the primary mirror and focus the light
How do astronomers deal with large mirrors in reflecting telescopes
They developed multi-mirror instruments and extremely thin mirrors
What are the 3 styles of reflectors
Prime focus, cassegrain focus, and Newtonian focus
How does a prime focus reflector work
Light comes in and bounces off the primary mirror into a mounted camera hanging in the middle of the telescope
How does a cassegrain focus reflector work
Light comes in and bounces off the primary mirror, and then bounces off again off of a hanging secondary mirror in the middle back to the observer
How does a Newtonian reflector work
Light comes in and bounces off the primary mirror, it then hits a diagonal hanging mirror in the middle and into the observers eyes
What is diffraction
It is when waves pass through a narrow opening
How does diffraction affect how we see an object
A diffracted point source of light appears as a point surrounded by rings of light. EX: the sun
What is resolving power and what limits it
Resolving power is the ability for a telescope to gather detail, it is limited by the wave nature of light and its diffraction
How can resolution be increased
It can be increased by a larger telescope diameter
How can a larger resolution diameter be achieved
By the use of an interferometer which simultaneously combines the observations from two or more widely spaced telescopes
What are the 3 ways of detecting light
The human eye, photographic film, electronic detectors
What is photographic film
It chemically stores data to increase sensitivity to dim light. Very inefficient as only 4% of photons are recorded
What are electronic detectors
Incoming photons strike an array of semiconductor pixels that are connected to a computer. Efficiencies of 75% possible
What are the non visible wavelengths and what emits them
Cold gas= emits radio, dust clouds= emit infrared, hot gases= x-rays
