U 1 AOS 1 EMR and Waves

Question 1

What is a wave?

Answer 1

A disturbance that travels through a medium from the source to the detector without any movement of matter.

Question 2

What are the two categories of waves?

Answer 2

• Mechanical waves
• Electromagnetic waves

Question 3

Do electromagnetic waves require a medium to propagate?

Answer 3

No, they can travel through a vacuum.

Question 4

What do mechanical waves require to propagate?

Answer 4

A medium, such as air or water.

Question 5

How do particles of matter behave in a wave?

Answer 5

They vibrate up and down or back and forth about their rest position, transferring energy.

Question 6

What type of waves transfer energy at regular intervals?

Answer 6

Periodic waves.

Question 7

What are transverse waves?

Answer 7

Waves where the disturbance is at right angles to the direction the wave is travelling.

Question 8

Give an example of a transverse wave.

Answer 8

Ripples on the water surface.

Question 9

What are longitudinal waves?

Answer 9

Waves where the disturbance is parallel to the direction the wave is travelling.

Question 10

Give an example of a longitudinal wave.

Answer 10

Sound wave travelling through air.

Question 11

What does frequency measure?

Answer 11

The number of times a wave repeats itself every second.

Question 12

What is the unit of frequency?

Answer 12

Hertz (Hz).

Question 13

What is the symbol for frequency?

Answer 13

f.

Question 14

What is the period of a wave?

Answer 14

The time it takes for a complete wave to pass a given point.

Question 15

What is the unit of period?

Answer 15

Seconds.

Question 16

What is the symbol for period?

Answer 16

T.

Question 17

What is amplitude?

Answer 17

The size of the maximum disturbance of the medium from its normal state.

Question 18

How is amplitude measured in sound waves?

Answer 18

In units of pressure.

Question 19

What is wavelength?

Answer 19

The distance between successive corresponding parts of a periodic wave.

Question 20

What is the symbol for wavelength?

Answer 20

λ (lambda).

Question 21

How is wavelength defined for transverse waves?

Answer 21

Distance between successive crests (or troughs).

Question 22

How is wavelength defined for longitudinal waves?

Answer 22

Distance between two successive compressions or rarefactions.

Question 23

What does the displacement–distance graph represent?

Answer 23

A snapshot of the wave at an instant in time.

Question 24

What is the universal wave equation?

Answer 24

v = fλ.

Question 25

What determines the frequency of a periodic wave?

Answer 25

The source of the wave.

Question 26

What determines the speed of a periodic wave?

Answer 26

The medium through which it is travelling.

Question 27

What are compressions in a longitudinal wave?

Answer 27

Regions in the medium where particles are closer together.

Question 28

What are rarefactions in a longitudinal wave?

Answer 28

Regions in the medium where particles are spread out.

Question 29

What is the hottest object in our environment?

Answer 29

The Sun ## Footnote The Sun is the primary source of energy for Earth.

Question 30

What phenomenon describes the light spectrum produced by hot objects?

Answer 30

Blackbody radiation ## Footnote This spectrum is characteristic of the temperature of the emitting body.

Question 31

What happens to a solid object when it is heated to several hundred degrees Celsius?

Answer 31

It becomes incandescent and glows ## Footnote Incandescence is the emission of light from a hot object.

Question 32

Define a blackbody.

Answer 32

A theoretically ideal object for producing incandescent light ## Footnote A blackbody is a perfect absorber and radiator of electromagnetic radiation.

Question 33

What does a theoretical blackbody do at low temperatures?

Answer 33

Absorbs all electromagnetic radiation ## Footnote It is a perfect absorber and does not reflect light.

Question 34

What is the surface temperature of the Sun?

Answer 34

Approximately 5500 °C ## Footnote This temperature influences the solar intensity emitted.

Question 35

Where does the highest intensity of the Sun's emission occur in the electromagnetic spectrum?

Answer 35

In the green part of the visible spectrum ## Footnote However, the total intensity is highest in the yellow part.

Question 36

What is the relationship between temperature and radiant energy absorption?

Answer 36

If an object absorbs more radiant energy than it emits, its temperature increases ## Footnote This principle is fundamental to thermal energy transfer.

Question 37

What factors affect the rate of emission and absorption of energy from an object?

Answer 37

Temperature of the object and surroundings, surface area, properties of the surface ## Footnote These factors influence how quickly energy is transferred.

Question 38

What type of objects are almost perfect absorbers of radiant energy?

Answer 38

Matte-black objects ## Footnote They absorb radiant energy of all wavelengths effectively.

Question 39

What do white and shiny objects do with radiant energy?

Answer 39

Re-emit a significant proportion of radiant energy from the visible spectrum ## Footnote These surfaces are less effective at absorbing energy.

Question 40

Fill in the blank: The formula to convert Celsius to Kelvin is _______.

Answer 40

K = °C + 273 ## Footnote This formula is used to convert temperature scales.

Question 41

True or False: All objects in everyday life are continually absorbing and emitting thermal energy.

Answer 41

True ## Footnote This is a fundamental property of matter.

Question 42

What does Maxwell's model of an electromagnetic wave propose?

Answer 42

A changing electric field produced by a charged particle moving backwards and forwards produces a changing magnetic field at right angles to it.

Question 43

How do the changing electric and magnetic fields propagate?

Answer 43

They self-propagate outwards, extending into space with both fields oscillating at the same frequency.

Question 44

What type of wave does Maxwell's model indicate electromagnetic radiation is?

Answer 44

A transverse wave.

Question 45

What did Maxwell's theory explain?

Answer 45

How light is produced and self-propagated through space as electromagnetic waves.

Question 46

What types of radiation does Maxwell's theory apply to?

Answer 46

Visible light, gamma rays, x-rays, infrared radiation, ultraviolet radiation, microwaves, and radio waves.

Question 47

What is the electromagnetic spectrum?

Answer 47

The range of all electromagnetic radiation of different wavelengths and frequencies.

Question 48

How does radiation travel?

Answer 48

As a form of energy that travels and spreads out in three dimensions from its source.

Question 49

What sections make up the electromagnetic spectrum?

Answer 49

* Radio waves * Microwaves * Infrared radiation * Visible light * Ultraviolet radiation * X-rays * Gamma rays

Question 50

How is visible light modeled?

Answer 50

As transverse waves with colors differing in frequency.

Question 51

Why is visible light visible to us?

Answer 51

Because its frequency, wavelength, and energy are 'just right' to interact with the retina of our eyes.

Question 52

Fill in the blank: Radiation with frequencies and wavelengths outside those of visible light interact differently with our _______.

Answer 52

body.