Flashcards in Physics Final Deck (134)

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1

## T/F Macro means bigger and micro means smaller

### True

2

## T/F The symbol for millions is mega and millionths is micro

### True

3

## T/F The symbol for hundreds is giga and the symbol for hundredths is hecto

### False; hundreds is hecto (h), hundredths is centi (c)

4

## T/F A wave with a frequency of 15,000 MHz is ultrasonic

### True

5

## T/F If the power of a wave is halved, the intensity is reduced to one-fourth its original value

### False; intensity is the power of a beam divided by its cross-sectional area. If we halve the power, we will halve the intensity

6

## T/F If the amplitude of a wave is increased to 3 times its original value, the intensity is increased by 6 times

### False; Intensity is proportional to the amplitude squared. If we triple the amplitude, we increase the intensity by a factor of nine.

7

## T/F Propagation speed is determined by the medium

### True

8

## T/F Propagation speed increases as frequency increases

### False; they are unrelated

9

## T/F We need one intensity to calculate decibels

### False; we need two intensities to calculate decibels

10

## T/F As the path length increases, attenuation of US in soft tissue increases

### True

11

## T/F Spatial peak intensity is always lower than the spatial average intensity

### False; Spatial peak intensity is always higher than the spatial average intensity

12

## T/F In addition to location within the beam, sound wave intensities also vary over time

### True

13

## T/F SPTA intensity is the most relevant intensity with respect to tissue heating

### True

14

## T/F The duty factor is a unit less number with a value between 0 and 1

### True

15

## T/F There are two different methods to measure and report intensities

### False; there are 6 different methods to measure and report intensities

16

## T/F The duty factor for a pulsed ultrasound system is 2%.

### False; with anatomic imaging the duty factor is 0.2%

17

## T/F An ultrasound beam has the same intensity at different depths or at different side to side locations within the beam

### False; the beam will have different intensities

18

## T/F At a particular depth, the center of a sound beam is more intense than the edges

### True

19

## T/F Temporal peak intensity is maximum in time

### True

20

## How many hertz is 3MHz?

### 3,000,000 Hz

21

## How much bigger is a billion than a million?

### 1,000

22

## What are the units of wavelength?

### unit of length, mm or m

23

## What are the units of frequency?

### Hertz; Hz

24

## What are the units of intensity?

### W/cm^2

25

## What are the units of propagation speed?

### units: m/s, mm/ μs, or any distance divided by time

26

## What are the units of period?

### units of time, microseconds, seconds, hours, or days

27

## Of the following which grouping is determined by the sound source?

###
Amplitude, power, intensity

Period, frequency

28

## If the intensity remains the same while the power is doubled, what happens to the beam area?

### Doubles

29

## A sound beam travels a total of 10cm in 2 seconds. What is the speed of the sound in this medium?

### 5cm/sec

30