2.4.1
Finding Frequency from Time Period
2.4.2
Finding Frequency from the number of waves and time taken
2.4.3
Finding Frequency from Wavelength and Wave Speed
2.5
References
2.5.1
AQA
2.5.2
Edexcel
2.6
References
The
frequency
of this
wave
can be found by counting the number of times the red marker
oscillates
every
second
.
-
The higher the
frequency
the quicker the
wave
oscillates
.
-
In
sound
frequency
is known as
pitch
. A high
pitch
is a high
frequency
.
-
In
light
frequency
affects the
colour
of the
light
. Red is a low
frequency
and violet is a high
frequency
.
Equation
Frequency = 1/(Period)
\(f = \frac{1}{T}\)
Where:
f =
Frequency
T =
time period
(the
time
it takes for one
wave
to pass a point).
Key Stage 4
Meaning
Frequency
is the number of
waves
that pass a given point in one
second
.
About Frequency
-
Frequency
is a
scalar
quantity because it has
magnitude
but no direction.
-
The
SI Unit
of
frequency
is
Hertz
(Hz).
Water Waves
The
frequency
of this
wave
can be found by counting the number of times the red marker
oscillates
every
second
.
-
The higher the
frequency
the quicker the
wave
oscillates
.
-
In
sound
frequency
is known as
pitch
. A high
pitch
is a high
frequency
.
-
In
light
frequency
affects the
colour
of the
light
. Red is a low
frequency
and violet is a high
frequency
.
-
When
wave
enters a new
medium
it will remain the same
frequency
but the
wave speed
and
wavelength
will change.
-
Frequency
can be found by counting the number of
waves
which pass a point in a given
time
and dividing this by the
time
.
Equation
Equation 1
NB: You do not need to remember this equation but you should know how to find
frequency
given the
time
taken for one
wave
to pass a point.
Frequency = 1/(Period)
\(f = \frac{1}{T}\)
Where:
f =
Frequency
T =
time period
(the
time
it takes for a wave to pass a point).
Equation 2
NB: You do not need to remember this equation but you should know how to find
frequency
given the number of
waves
passing a point and the
time
taken.
Frequency = (Number of Waves which pass a point)/(Time taken for waves to pass a point)
\(f = \frac{n}{t}\)
Where:
f =
Frequency
n = Number of
waves
which pass a point.
t = The
time
taken for those
waves
to pass a point.
Equation 3
NB: You should remember this equation with v as the subject of the formula.
Frequency = (Wave Speed)/(Wavelength)
\( f = \frac{v}{\lambda}\)
Where
\( \lambda\) = The
wavelength
of the
wave
.
\(v\) = The
wave speed
of the
wave
.
\(f\) = The
frequency
of the
wave
.
Example Calculations
Finding Frequency from Time Period
Calculate the
frequency
of a
wave
with a
period
of 0.04 seconds.
A giant pendulum takes 16 seconds to make one complete
oscillation
. Calculate the
frequency
of the pendulum.
1. State the known quantities
T = 0.04s
1. State the known quantities
T = 16s
2.
Substitute
the numbers into the
equation
and
solve
.
\( f = \frac{1}{T}\)
\( f = \frac{1}{0.04}\)
\( f = 25Hz\)
2.
Substitute
the numbers into the
equation
and
solve
.
\( f = \frac{1}{T}\)
\( f = \frac{1}{16}\)
\( f = 0.0625Hz\)
Finding Frequency from the number of waves and time taken
A scientist wants to determine the
frequency
of a pendulum. They count that the pendulum
oscillates
15 times over 20 seconds. Calculate the
frequency
of the pendulum.
A sailor notices a buoy bounce up and down 24 times over a minute. Calculate the
frequency
of the
waves
.
1. State the known quantities
n = 15
t = 20s
1. State the known quantities
n = 24
t = 60
2.
Substitute
the numbers into the
equation
and
solve
.
\(f = \frac{n}{t}\)
\(f = \frac{15}{20}\)
\(f = 0.75Hz\)
2.
Substitute
the numbers into the
equation
and
solve
.
\(f = \frac{n}{t}\)
\(f = \frac{24}{60}\)
\(f = 0.4Hz\)
Finding Frequency from Wavelength and Wave Speed
A
microwave
travelling at a speed of 3.0x10
8
m/s has a
wavelength
of 0.051m. Calculate the
frequency
of the
wave
correct to two
significant figures
.
An
ultrasound
wave
of
wavelength
0.125m passes through an
Iron
block at a
speed
of 5000m/s. Calculate the
frequency
of the
wave
correct to two
significant figures
.
1. State the known quantities
v = 3.0x10
8
m/s
λ = 0.051m
1. State the known quantities
v = 5000m/s
λ = 0.125m
2.
Substitute
the numbers into the
equation
and
solve
.
\( f = \frac{v}{\lambda}\)
\( f = \frac{3.0 \times 10^8}{0.051}\)
\( f = 5882352941Hz\)
\( f \approx 5900000000Hz\)
2.
Substitute
the numbers into the
equation
and
solve
.
\( f = \frac{v}{\lambda}\)
\( f = \frac{5000}{0.125}\)
\( f = 40000Hz\)
References
-
Frequency (f), pages 50-1, 583, GCSE Physics, Hodder, AQA
-
Frequency, page 73, GCSE Physics; The Revision Guide, CGP, AQA
-
Frequency, pages 189, 190, GCSE Combined Science Trilogy; Physics, CGP, AQA
-
Frequency, pages 190-3, 200-1, 206-9, 213-15, 218, 222, 224, 236-7, 275, GCSE Physics; Student Book, Collins, AQA
-
Frequency, pages 226, 227, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
-
Frequency, pages 257, GCSE Combined Science Trilogy 2, Hodder, AQA
-
Frequency; human hearing range, page 280, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
-
Frequency; human hearing range, page 88, GCSE Physics; The Revision Guide, CGP, AQA
-
Frequency; Measurement of, pages 260, GCSE Combined Science Trilogy 2, Hodder, AQA
-
Frequency; of EM waves, pages 200, 203, GCSE Combined Science Trilogy; Physics, CGP, AQA
-
Frequency; of EM waves, pages 242, 245, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
-
Frequency; of EM waves, pages 76, 81, GCSE Physics; The Revision Guide, CGP, AQA
-
Frequency; of mains electricity, page 66, GCSE Physics; Student Book, Collins, AQA
-
Frequency; of mains supply, page 31, GCSE Physics; The Revision Guide, CGP, AQA
-
Frequency; of mains supply, page 86, GCSE Combined Science Trilogy; Physics, CGP, AQA
-
Frequency; of mains supply, page 89, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
-
Frequency; table, pages 40-1, GCSE Physics; Student Book, Collins, AQA
Edexcel
-
Frequency (waves), page 91, GCSE Physics, CGP, Edexcel
-
Frequency (waves); of hearing, page 104, GCSE Physics, CGP, Edexcel
-
Frequency (waves); of infrasound, page 109, GCSE Physics, CGP, Edexcel
-
Frequency (waves); of ultrasound, page 106, GCSE Physics, CGP, Edexcel
-
Frequency, pages 164-166, 168, GCSE Combined Science; The Revision Guide, CGP, Edexcel
-
Frequency, pages 32-34, 43, GCSE Physics; The Revision Guide, CGP, Edexcel
-
Frequency, pages 331, 340, GCSE Combined Science, Pearson Edexcel
-
Frequency, pages 49, 72, GCSE Physics, Pearson Edexcel
References
-
Frequency, pages 137, 142, 149, , 153, 179, 256-157, Gateway GCSE Physics, Oxford, OCR
-
Frequency, pages 186-188, Gateway GCSE Combined Science; The Revision Guide, CGP, OCR
-
Frequency, pages 59-61, 64, Gateway GCSE Physics; The Revision Guide, CGP, OCR
