DLISC1 - week 12

Question 1

what is a vibration

Answer 1

• The source of all wave motion is a vibration

Question 2

what is a wave

Answer 2

• A wave is a disturbance that carries energy through matter (a medium) or space
• waves transmit energy not matter

Question 3

types of waves

Answer 3

• Electromagnetic waves: waves that can travel trough empty space. They do not require a medium
• Mechanical waves: waves that must travel through some from of matter to carry their energy

Question 4

properties of a wave

Answer 4

• Amplitude
• Wavelength
• Crest
• Trough
• Period
• Frequency

Question 5

what is an amplitude

Answer 5

Maximum displacement from equilibrium. The larger the amplitude, the more energy the wave carries.

Question 6

what is a wavelength

Answer 6

The distance between successive identical parts of a wave. Represented by lambda

Question 7

what is a crest

Answer 7

the high point of a wave

Question 8

what is a trough

Answer 8

the low point of a wave

Question 9

what is a period

Answer 9

the time needed for a wave to make one complete cycle (wavelength) of motion. represented by T. units of seconsd

Question 10

what is a frequency

Answer 10

number of cycles (wavelengths) per unit of time. represented by f. units of hertz.

Question 11

calculate the frequency of a pendulum that has a period of 1/4 second

Answer 11

f = 1 / T = 1 / (0.25 s) = 4 Hz

Question 12

the equation for the speed of waves

Answer 12

speed = distanace/time

Question 13

how do waves interact wiht matter

Answer 13

1. absorption
2. reflection
3. refraction and diffraction
4. interference

Question 14

wave interactions - absorption

Answer 14

this occurs when a wave transfers it’s energy to a material. An example of this is when the sun emits light rays which are absorbed by the skin which can cause damage.

Question 15

wave interactions - reflection

Answer 15

this occurs when a wave bounces off a material and travels in a different direction.

Question 16

wave interactions - refraction and diffraction

Answer 16

this occurs when a wave passes through a material. This is called the transmission of waves. Waves can be transmitted through many different mediums like solids, liquids and gasses.

Question 17

wave interactions - interference

Answer 17

this is a phenomena that occurs when two waves met while traveling along the same medium. There are two types of interferences in waves, constructive and destructive.

Question 18

what are sound waves

Answer 18

• Sound waves are caused by vibrations of material objects.
• Sound waves require a medium. Sound cannot travel through a vacuum.

Question 19

what is the ‘normal’ hearing frequency range of a healthy young person

Answer 19

20 to 20,000Hz

Question 20

sound in air

Answer 20

• Sound is a mechanical wave, resulting from the vibration of the particles of the medium through which the wave is moving. The medium doesn’t travel, it is the vibration pulse that does.
• Sound waves in air are longitudinal

Question 21

speed of sound

Answer 21

• The speed of sound in a material depends not on the material’s density, but on its elasticity.
• Elasticity is the ability of a material to change shape in response to an applied force, and then resume its initial shape once the distorting force is removed.

Question 22

what is the doppler effect

Answer 22

• The Doppler effect is the change in observed frequency due to the motion of the source in respect to an observer.
  Higher frequency: Object approaching
  Lower frequency: Object receding

Question 23

retina consists of:

Answer 23

• Rods – can sense light but not colour.
• Cones – can sense colour but not light.
  Red Cones
  Green Cones
  Blue Cone

Question 24

how do we see colour

Answer 24

The colour of an object is not actually within the object itself. Rather, the colour is in the light that shines upon it and is ultimately reflected to our eyes.

Question 25

what are the primary colours

Answer 25

red, green and blue

Question 26

what contorls colour blindness

Answer 26

- Colour blindness is found in 4% of the male population and 0.25% of the female population. - Color blindness is a sex linked recessive genetic trait that appears on the X chromosome. - Since men have only one X chromosome, if the gene for color blindness appears on it, they will be color blind. - Women have two X chromosomes and it would have to appear on both X chromosomes before the woman would exhibit the trait

Question 28

what are the effects of gravity on the body

Answer 28

- One of the important medical effects if gravitational force is the formation of varicose veins in the legs as the venous blood travels against the force of gravity on it's way to the heart. - Another medical effect of gravity is on the bones. Bone loses some bone mineral when a person becomes weightless such in an orbiting satellite, this may be a serious problem on very long space journeys.

Question 29

electrical forces on the body

Answer 29

- Our bodies are basically electrical machines. The forces produced by the muscles are caused by electrical charges attracting or repelling other electrical charges. - Control and action of our muscles is primarily electrical. - Cells in the body has an electrical potential difference across the cell membrane.

Question 30

frictional forces on the body

Answer 30

Frictional force refers to the force generated by two surfaces that contacts and slide against each other - Friction and the energy loss die to friction, appear everywhere in our everyday life - Friction between two surfaces produces a frictional reaction force that opposes motion - Synovial fluid in the bone joint helps in lubrication

Question 31

the effect of acceleration on the body

Answer 31

1. An apparent increase or decrease in body weight 2. Changes in the internal hydrostatic pressure 3. Distortion of the elastic tissues of the body, and if the forces are very large, tearing can take place 4. If the acceleration becomes large, the body will lose control because it does not have the adequate muscle force to work against the larger acceleration force 5. Under certain condition, the blood may pool in various regions of the body, the location of pooling depends upon the direction of acceleration. If the person accelerated in the head lack of blood flow of the brain can cause blackout and unconsciousness