Name:
2.4.4 – Microwave Properties Exam Question - Self Assessed HW
Mark
...... / ........
.......%
Grade.........
AO1) Knowledge and
understanding of
science and how
science works
AO2) Application of
Skills, Knowledge
and Understanding
AO3) Practical,
Enquiry and Data
Handling Skills
BASIC LEVEL
1.
The figure below shows an arrangement that can be used to determine the wavelength
of microwaves.
metal plate
D
T
P
transmitter
Microwaves leave the transmitter and move in a direction TP which is at right angles to
the metal plate. A standing (stationary) wave is formed between T and P.
(i)
State what is meant by a standing wave and explain how it is formed in this case.
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HIGHER LEVEL
(ii)
When a small microwave detector D is moved slowly from T towards P the signal
received changes from strong to weak to strong to weak etc. The distance between
the positions of neighbouring weak signals is 1.4 cm.
Calculate for these microwaves
1
the wavelength
wavelength = ................ cm
[1]
2
the frequency.
frequency = .............. Hz
[2]
(iii) Describe how you could test whether the microwaves leaving the transmitter were
plane polarised.
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[2]
[Total 8 marks]
Mr Powell 2012
Markscheme
2.
(i)
it consists of nodes and antinodes / it does not transfer energy (WTTE)B1
formed by two identical waves travelling in opposite directions (WTTE)
B1
(microwaves leaving transmitter) interfere (with reflected waves) (WTTE)
B1
{allow superimpose/interact/cancel out/reinforce for interfere}
(ii)
1.wavelength of the microwaves = 2  1.4 = 2.8 cm
2. speed of microwaves in air = 3 × 108 m/s OR c
frequency = 3 × 108 /2.8 × 10 – 2 (allow ecf) = 1.07  1010 Hz
B1
M1
A1
(iii) Place a metal grid {allow “Polaroid”} (between T and D) and rotate
(or place at 90) OR rotate grid/transmitter/detector
B1
this causes minm/zero signal (WTTE)
B1
[8]
Mr Powell 2012