Week 5 Light(1) Flashcards
What is light?
Light comes in many colors and is a wave of electricity and magnetism
Light can be described in terms of its wave properties, such as wavelength and frequency.
What is the speed of light?
300,000,000 m/s
This is often denoted as ‘c’ in physics equations.
What does it mean that light is quantized?
Light cannot be created in any size (energy) only in specific packages of energy called photons.
This concept is a fundamental principle of quantum mechanics.
What is the formula for energy in relation to frequency?
E = hf
‘h’ is Planck’s constant, approximately 6.62607015×10⁻³⁴ joule/hertz.
What does the wavelength represent?
The length of one cycle of a wave.
What does frequency measure?
The number of cycles per second.
What is the law of reflection?
The angle of reflection equals the angle of incidence (θr = θi).
What is refraction?
It is the bending of light when it crosses a boundary between different media.
What happens when light crosses a boundary where the speed of light decreases?
The ray bends toward the perpendicular line.
What is a positive lens?
A lens that converges rays of light to a focal point.
What is a negative lens?
A lens that diverges rays of light, making them appear to originate from a focal point.
What is a real image?
An image that can be projected onto a screen.
What is a virtual image?
An image that cannot be projected; it appears upright and is located closer to the lens than the object.
How does a camera obscura work?
It uses a pinhole to project an image onto a screen.
What is chromatic aberration?
A distortion in color due to the different wavelengths of light being focused at different points.
What is a parabolic mirror?
A mirror that focuses light to a single point, used in large telescopes.
What are the primary colors needed for color photography?
- Red
- Green
- Blue
What is spectroscopy?
The measurement of the frequencies of light to analyze the spectrum.
What is the function of a telescope’s aperture?
It determines how much light comes into the telescope.
What is the diffraction limit?
The limit imposed by the wave nature of light on the resolution of images.
Fill in the blank: Light is a _______ which spreads out in all directions.
wave
True or False: A diverging lens has a positive focal length.
False
What are the main concerns when building a telescope?
- Diameter (aperture)
- Magnification
- Stability
What technique is used to project a real image in a camera?
Light rays are focused onto a film or sensor.
What happens when light hits a rough surface?
It is diffused and reflected at many different angles.
What is the focal point of a lens?
The point where parallel rays of light converge.
What does a digital camera use to create an image?
A grid of pixels.
What is the purpose of RGB filters in telescopes?
To separate and analyze different wavelengths of light.
What is the main requirement for ground-based telescopes?
Dry, clear, cool conditions
Ground-based telescopes perform best in environments that minimize atmospheric interference.
Where are the best locations for ground-based telescopes?
Desert mountain tops
High altitude locations help reduce atmospheric disturbances.
Why do some wavelengths need to be measured from space?
They do not pass through the atmosphere
Certain wavelengths, like X-rays and gamma rays, are absorbed by the atmosphere, necessitating space-based observatories.
How does the visibility of the sky change with latitude?
At the equator, most of the sky is visible; at the poles, visibility decreases
Northern latitudes allow visibility of the North Pole but not the South Pole.
What is the size of the Keck Observatory in Hawaii?
10m
The Keck Observatory operates twin telescopes for VIS/IR observations.
What is the significance of spectral lines in astronomy?
They provide information about composition and motion
Spectral lines can indicate the elements present in a star and its relative motion.
What is a Black Body Spectrum?
The spectrum produced by hot objects
This spectrum shows the distribution of light emitted across various frequencies, peaking at a specific wavelength determined by temperature.
What are the main processes through which light can be produced?
- Atoms emitting light
- Hot objects
- Accelerated electric charges
Each process results in different types of light spectra, such as atomic spectra and black body radiation.
What is the formula for calculating peak wavelength in black body radiation?
b = 2.898 x 10^-3 mK
This formula relates temperature (in Kelvin) to the peak wavelength of emitted radiation.
What happens to light as it spreads out from its source?
It gets fainter
The apparent brightness of light decreases with distance from the source.
True or False: The speed of light varies depending on the observer’s speed.
False
All observers measure the speed of light to be the same, regardless of their relative motion.
What is the effect of motion on the light spectrum from sources moving towards or away from us?
- Light from approaching sources shifts to the blue side
- Light from receding sources shifts to the red side
This phenomenon is known as redshift and blueshift, indicating the relative motion of celestial objects.
What is the size of the Arecibo Observatory?
300m (retired)
The Arecibo Observatory was a significant radio telescope before its retirement.
Fill in the blank: The _____ is the largest single-dish radio telescope currently operational.
FAST
FAST in China has a diameter of 500m and is currently the largest single-dish radio telescope.
What type of array is the SKA?
Radio Array
The SKA (Square Kilometre Array) consists of numerous antennas designed for radio astronomy.
