Week 5 Light(1)

Question 1

What is light?

Answer 1

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.

Question 2

What is the speed of light?

Answer 2

300,000,000 m/s

This is often denoted as ‘c’ in physics equations.

Question 3

What does it mean that light is quantized?

Answer 3

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.

Question 4

What is the formula for energy in relation to frequency?

Answer 4

E = hf

‘h’ is Planck’s constant, approximately 6.62607015×10⁻³⁴ joule/hertz.

Question 5

What does the wavelength represent?

Answer 5

The length of one cycle of a wave.

Question 6

What does frequency measure?

Answer 6

The number of cycles per second.

Question 7

What is the law of reflection?

Answer 7

The angle of reflection equals the angle of incidence (θr = θi).

Question 8

What is refraction?

Answer 8

It is the bending of light when it crosses a boundary between different media.

Question 9

What happens when light crosses a boundary where the speed of light decreases?

Answer 9

The ray bends toward the perpendicular line.

Question 10

What is a positive lens?

Answer 10

A lens that converges rays of light to a focal point.

Question 11

What is a negative lens?

Answer 11

A lens that diverges rays of light, making them appear to originate from a focal point.

Question 12

What is a real image?

Answer 12

An image that can be projected onto a screen.

Question 13

What is a virtual image?

Answer 13

An image that cannot be projected; it appears upright and is located closer to the lens than the object.

Question 14

How does a camera obscura work?

Answer 14

It uses a pinhole to project an image onto a screen.

Question 15

What is chromatic aberration?

Answer 15

A distortion in color due to the different wavelengths of light being focused at different points.

Question 16

What is a parabolic mirror?

Answer 16

A mirror that focuses light to a single point, used in large telescopes.

Question 17

What are the primary colors needed for color photography?

Answer 17

• Red
• Green
• Blue

Question 18

What is spectroscopy?

Answer 18

The measurement of the frequencies of light to analyze the spectrum.

Question 19

What is the function of a telescope’s aperture?

Answer 19

It determines how much light comes into the telescope.

Question 20

What is the diffraction limit?

Answer 20

The limit imposed by the wave nature of light on the resolution of images.

Question 21

Fill in the blank: Light is a _______ which spreads out in all directions.

Answer 21

wave

Question 22

True or False: A diverging lens has a positive focal length.

Answer 22

False

Question 23

What are the main concerns when building a telescope?

Answer 23

• Diameter (aperture)
• Magnification
• Stability

Question 24

What technique is used to project a real image in a camera?

Answer 24

Light rays are focused onto a film or sensor.

Question 25

What happens when light hits a rough surface?

Answer 25

It is diffused and reflected at many different angles.

Question 26

What is the focal point of a lens?

Answer 26

The point where parallel rays of light converge.

Question 27

What does a digital camera use to create an image?

Answer 27

A grid of pixels.

Question 28

What is the purpose of RGB filters in telescopes?

Answer 28

To separate and analyze different wavelengths of light.

Question 29

What is the main requirement for ground-based telescopes?

Answer 29

Dry, clear, cool conditions ## Footnote Ground-based telescopes perform best in environments that minimize atmospheric interference.

Question 30

Where are the best locations for ground-based telescopes?

Answer 30

Desert mountain tops ## Footnote High altitude locations help reduce atmospheric disturbances.

Question 31

Why do some wavelengths need to be measured from space?

Answer 31

They do not pass through the atmosphere ## Footnote Certain wavelengths, like X-rays and gamma rays, are absorbed by the atmosphere, necessitating space-based observatories.

Question 32

How does the visibility of the sky change with latitude?

Answer 32

At the equator, most of the sky is visible; at the poles, visibility decreases ## Footnote Northern latitudes allow visibility of the North Pole but not the South Pole.

Question 33

What is the size of the Keck Observatory in Hawaii?

Answer 33

10m ## Footnote The Keck Observatory operates twin telescopes for VIS/IR observations.

Question 34

What is the significance of spectral lines in astronomy?

Answer 34

They provide information about composition and motion ## Footnote Spectral lines can indicate the elements present in a star and its relative motion.

Question 35

What is a Black Body Spectrum?

Answer 35

The spectrum produced by hot objects ## Footnote This spectrum shows the distribution of light emitted across various frequencies, peaking at a specific wavelength determined by temperature.

Question 36

What are the main processes through which light can be produced?

Answer 36

* Atoms emitting light * Hot objects * Accelerated electric charges ## Footnote Each process results in different types of light spectra, such as atomic spectra and black body radiation.

Question 37

What is the formula for calculating peak wavelength in black body radiation?

Answer 37

b = 2.898 x 10^-3 mK ## Footnote This formula relates temperature (in Kelvin) to the peak wavelength of emitted radiation.

Question 38

What happens to light as it spreads out from its source?

Answer 38

It gets fainter ## Footnote The apparent brightness of light decreases with distance from the source.

Question 39

True or False: The speed of light varies depending on the observer's speed.

Answer 39

False ## Footnote All observers measure the speed of light to be the same, regardless of their relative motion.

Question 40

What is the effect of motion on the light spectrum from sources moving towards or away from us?

Answer 40

* Light from approaching sources shifts to the blue side * Light from receding sources shifts to the red side ## Footnote This phenomenon is known as redshift and blueshift, indicating the relative motion of celestial objects.

Question 41

What is the size of the Arecibo Observatory?

Answer 41

300m (retired) ## Footnote The Arecibo Observatory was a significant radio telescope before its retirement.

Question 42

Fill in the blank: The _____ is the largest single-dish radio telescope currently operational.

Answer 42

FAST ## Footnote FAST in China has a diameter of 500m and is currently the largest single-dish radio telescope.

Question 43

What type of array is the SKA?

Answer 43

Radio Array ## Footnote The SKA (Square Kilometre Array) consists of numerous antennas designed for radio astronomy.