Light

Question 1

Electromagnetic waves

Answer 1

Waves made form vibrating electric and magnetic fields that regenerate each other. These waves emanate (move outward) from the vibrating charge

Question 2

Electromagnetic waves velocity

Answer 2

Electromagnetic wave traveling through space never changes its speed - gravity can change the frequency of light or deflect light, bit it can’t change the speed of light

Question 3

Radiation frequency

Answer 3

Light is electromagnetic radiation within a particular frequncy range 4.3 x 10^14 to 7 x 10^14 vibrations per second ROYGBIV Red is low frequency (long wavelength)

Question 4

Electromagnetic spectrum

Answer 4

Classification of electromagnetic waves according to frequency - kHz = low frequency radio waves - MHz = middle of AM radio band - 80-108 MHz = FM radio band - 50 MHz = very high frequency (VHF) ** The frequency of an electromagnetic wave as it vibrates through space is identical to the frequency of the oscillating electric charge generating it. - higher the frequency of the vibrating charge, the shorter the wavelength of radiant energy

Question 5

Electromagnetic spectrum parts

Answer 5

Radio - microwaves - infrared - visible (ROYGBIV) - ultraviolet, x-ray, gamma ray

Question 6

Transparent materials

Answer 6

Light is an energy-carrying electromagnetic wave that emanates from vibrating electrons in atoms - the way a receiving material responds when light is incident upon it depends on the frequency of the light and on the natural frequency of the electronss in the material - lass and water allow light to pass though in straight lines

Question 7

Light speed in transparent materials

Answer 7

C = speed of light (300,000 km/sec) - glass = 0.67c - water = 0.75c - diamond = 0.41c When emerging back into air, it returns to c

Question 8

Opaque materials

Answer 8

Light is absorbed without reemitting it - vibrations given by light to their atoms and molecules are turned into random kinetic energy (internal energy) - in metal, when light shines on it, electrons vibrate and reflect (shiny appearance) - earth’s atmosphere is opaque to high-frequency UV light

Question 9

Opaque materials cont

Answer 9

Light incident on a wet surface bounce around inside the transparent wet region before it reaches your eyes, more absorption of light to the wet surface = image of darker surface

Question 10

Excitation

Answer 10

A more distant electron from the nucleus is in a “higher energy state” or at a “higher energy level” - when many atoms in a material are excited, many photons with many frequencies are emitted that correspond to many different levels excited - characteristic colors of light (neon)

Question 11

Excited

Answer 11

When an electron is raised to a higher energy level

Question 12

De-excitation

Answer 12

This is temporary and returns to its lower energy state while emitting radiant energy ** light is emitted when an electron in an atom makes a “quantum jump” form a a higher to a lower energy level

Question 13

Photon

Answer 13

Pulse of electromagnetic radiation caused by electrons dropping from higher to lower energy levels in an excited atom - frequency of a photon is directly proportional to its energy

Question 14

Emission spectrum

Answer 14

Distribution of wavelengths in the light from a luminous source - each element has its own characteristic pattern of electron energy levels and emits light with its own characteristic pattern of frequencies

Question 15

Emission spectra

Answer 15

• each component color is focused at a definite position, according to its frequency. A given frequency corresponds to a definite wavelength - therefore, colors are referred to in terms of their wavelength

Question 16

Incandescence

Answer 16

Light that is produced as a result of high temperature - it is a form of thermal radiation - contains an infinite number of frequencies, spread smoothly across the spectrum

Question 17

Absorption spectra

Answer 17

• continuous spectrum interrupted by dark lines or bands that result from the absorption of ight of certain frequencies by a substance through which the radiant energy passes - atoms will most strongly absorb light having the frequencies to which it is tuned - the positions of the dark lines correspond exactly to the positions of lines in an emission spectrum of the same gas - we determine speed of stars by studying the spectra the emit

Question 18

Fluorescence

Answer 18

Property of certain substances to absorb radiation of one frequency and to re-emit radiation of lower frequency - it occurs when an atom is boosted up to an excited state and loses its energy in two or more downward jumps to a lower energy state

Question 19

Phosphorescence

Answer 19

A type of light emission that is the same as fluorescence except for a delay between excitation and de-excitation, which provides an afterglow - due to atoms being excited to energy states that do not defy rapidly - glow in the dark objects

Question 20

Lasers

Answer 20

Light Amplification by Stimulated Emission of Radiation - devices that produce a beam of coherent light - beam of photons of the same frequency, phase, and direction - beam spreads and weakenes very little - all lasers have an active medium (gas, liquid, solid

Question 21

Lasers cont

Answer 21

• the atoms are excited by an external energy source. When a single photon from an atom that undergoes de-excitation can start a chain reaction such that another atom is struck and stimulating it into emission - light is initially moving in random directions, but is reflected by mirrors. The light that escapes through the more transparent-mirrored end makes up the laser beam

Question 22

Present lasers

Answer 22

• produce beams from infrared through UV - it is not a source of energy, it is a converter of energy - laser-light frequency are much higher frequencies than radio or television and therefore can carry more info (bar code)

Question 23

Lasers used medically

Answer 23

• microsurgery - kill cancer cells - interstitial lastre coagulation - pain relief (stimulates release of endorphins) - stimulates health and growth of new tissues

Question 24

Answer 24