P5.1 grey - new

Question 1

There are 2 ways to represent a wave

Answer 1

1 - a time trace shows how displacement varies with time at a particular position
2 - a snapshot of a wave shows how displacement varies with distance at a particular time

Question 2

Time trace - time for a wave to complete one oscillation is?

/ point for a wave to same point on next wave

Answer 2

Time period of the wave

Question 3

Snapshot - distance from one point on a wave to the same point on the next is?

Answer 3

Wavelength

Question 4

Amplitude in time trace / snapshot

Answer 4

Middle to the top/bottom(trough) of a wave

Question 5

To measure the velocity of sound - clap

Answer 5

Time how long it takes to hear an echo of a clap when yo are at a distance from a wall , work out velocity - distance, velocity, time

Question 6

To measure the velocity of sound - alternate

Answer 6

Connect a pair of microphones a certain distance apart to an oscilloscope
- know the distance between the microphones and the time for the sound to travel between them to calculate velocity

Question 7

As sound is a longitudinal wave, when you see the trace of a transverse wave on the screen of an oscilloscope, it is showing ?

Answer 7

Variation of pressure with time, not the sound wave itself

Question 8

The velocity of sound can vary w/ (2) and why

Answer 8

• temperature and pressure
• this is because these factors affect the velocity at which the disturbance in the wave is transferred between particles

Question 9

3 wave phenomena

Answer 9

Reflection - waves reverse direction
Refraction - waves change direction/bend
Diffraction - waves spread out

Question 10

Medium

Answer 10

(Plural media) is a region of space of the same material/density

Question 11

Wave phenomena only occur when (2)

Answer 11

• at the boundary between 2 media
• when a wave changes speed

Question 12

When waves cross a boundary, what changes, what doesnt

Answer 12

• speed will change
• frequency never changes
• wavelength will change
  (According to wave equation, as speed changes)

Question 13

Reflection - definition

Answer 13

Reflection is the wave phenomenon by which a wave reverses direction as it meets the boundary between two media.

Question 14

Reflection - rules

(2)

Answer 14

We always consider plane (smooth) surfaces such as mirrors, which obey the law of reflection.

“The angle of incidence, i is equal to the angle of reflection, r”

i = r

Question 15

PIC

Reflection - 1 line, 2 rays, 2 angles
W/ray diagram

Answer 15

.

Question 16

Plane mirror

Answer 16

A mirror which is perfectly flat( and reflects all of the light incident upon it)

Question 17

Law of reflection

Answer 17

“The angle of incidence, i is equal to the angle of reflection, r”

i = r
- true only for planer mirrors

Question 18

The image formed by a mirror can be shown using __

You need __ from the object .
You then ____ back into the mirror

Answer 18

Ray diagram

2 incident rays from the object

Project the 2 reflected rays back into the mirror

Question 19

P5.3.1

PIC

Answer 19

PIC

Question 20

If the angle of reflection of a light ray from a plane mirror is 20, what is;

the angle of incidence?
the angle between the incident ray and the reflected ray?

Answer 20

20 by The Law of Reflection

40

Question 21

REFRACTION DEFINE

Answer 21

Refraction is the wave phenomenon by which a wave changes direction (bends) as it crosses the boundary between two media.

Question 22

Refraction explanation

Answer 22

As waves cross a boundary between two different media… … their speed changes… … their direction changes… … they are observed to bend.

Question 23

PIC

REFRACTION RAY DIAGRAM from air to glass

Answer 23

PIC

Question 24

Refraction - 2 rules

Answer 24

Waves bend TOWARDS THE NORMAL when they pass from less dense to more dense medium (when they slow down)

Waves bend AWAY FROM THE NORMAL when they pass from more dense to less dense medium (when they speed up)

Question 25

COMPLETE PIC

Answer 25

PIC

Question 26

Ultrasound - what (+ consideration)

Answer 26

The name given to sound waves with a frequency grater than 20,000Hz

Can’t be heard because outside human audible range of 20Hz - 20 kHz

Question 27

Ultrasound scans -2 uses

PIC

Answer 27

• to image a baby inside a womb
• detecting cracks is in metal pipes and buildings

Question 28

How ultrasound scans work (3)

PIC

Answer 28

• the transducer is a device that produces ultrasound waves by causing a crystal to vibrate very rapidly
• the ultrasound waves are partially reflected every time they cross a boundary between different media
• the reflected ultrasound waves return to the transducer as a series of pulses, which are deciphered to form an image (the machine calculates the distance using time and velocity, and uses those distances to produce an image)

Question 29

An o__ t__ of ultrasound wave echoes can be used to calculate the __/__/__ of the various __ and __.

Answer 29

An oscilloscope trace of ultrasound wave echoes can be used to calculate the distance/depths/lengths of the various tissues and boundaries.

Question 30

PIC

Pulses in an oscilloscope (2)

Answer 30

The first recorded pulse is always the reflection of the transmitted pulse as it crosses into the body.

Pulses after that originate from reflections at boundaries.

Question 31

Depth of boundary - equation

Answer 31

= (speed of the ultrasound waves) x (transit time) x ½

Question 32

Sonar

Answer 32

Used by submarines and fishermen to find distances using the time for an echo and the speed of sound in water.

Question 33

Doctors also use ultrasound to -2

Answer 33

Find kidney stones, and monitor blood flow

Question 34

Whenever light passes between media along the normal line…

Answer 34

It doesn’t refract ,.. it passes straight through

Question 35

The ear is designed to - 3

Answer 35

Detect, amplify, and convert sound to an electrical signal

Question 36

How the ear detects sound - 5 steps

Answer 36

1- the pinna and auditory canal gather the sound wave; direct sound into the ear drum
2- the ear drum vibrates, and causes the ossicles to vibrate; vibrations of sound wave amplified
3- cochlea transmits vibrations to small hairs
4- hairs are attached to sound-detecting cells
5- cells release chemicals when stimulated, electrical signal sent to brain via auditory nerve

Question 37

Why does the human ear have an audible range - 4

Answer 37

• Any body that vibrates, has a natural frequency.
• The natural frequency of an object is the frequencyat which it can (physically) vibrate.
• The human ear drum can only vibrate between 20Hz and 20,000Hz… it is unable to vibrate any slower or faster than these limits.
• Thus, the human audible range is only 20hz-20,000Hz

Question 38

Why sound dies away- wal;

Answer 38

Absorbed
When sound absorbed, it makes the particles in the wall vibrate —> wall gets bit hotter

Question 39

When a microphone absorbs sound wave?

Answer 39

Diaphragm can move —> produces a changing electrical signal

Question 40

explain why such processes only work over a limited frequency range, and the relevance of this to human hearing

Answer 40

The hairs in the human cochlea have different lengths and vibrate at different frequencies of sound. This is how the human ear puts together an electrical signal that contains all the different frequencies in the sound wave being received.

The range of frequencies that a person can hear depends on the range of lengths of hairs in the cochlea.

Question 41

why hearing (audition) changes due to ageing

Answer 41

As a person ages, the shorter hairs that respond to higher frequencies stop working - this means that people tend to lose the ability to hear higher frequencies of sound as they grow older.

Question 42

Resonance

Answer 42

Applying a vibration at natural frequency, will result in a vibration with a very big amplitude - called resonance