Page 29 - Spotlight A+ Physics Form 4.5

Form
5
Chapter 7 Quantum Physics Physics
Table 12 shows nine electronic components and gadgets that may be connected to complete the
electronic eye system circuit.
Table 12

Capacitor Photodiode Thermistor
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©PAN ASIA PUBLICATIONS

9 V d.c. power supply Resistor Electromagnetic coil

240 V a.c. power supply Alarm Variable resistor

Using the knowledge of physics, choose any six suitable electronic components and gadgets in Table 12
to complete the circuit in Figure 12.2. Give reasons for your choice. C6 [12 marks]

Reinforcement & Assessment of Science Process Skills

1. You are required to carry out an experiment to determine the value of Planck’s constant.
(a) Carry out the experiment by using the steps below:
(i) Use five LEDs of different colors whereby their
wavelengths were taken from the manufacturer’s
catalogue. The threshold voltage, V is the potential +
difference across the LED when it begins to conduct
is measured by adjusting the potentiometer to set the 6 V d.c.
value of ammeter to zero. –
(ii) The values of the wavelengths for the five LEDs are V
λ = 467 nm, 567 nm, 586 nm, 623 nm and 793 nm as A
labelled on them.
(iii) Tabulate your readings in a table for all values of λ, V Figure 1.1
1
and –—.
λ
Table 1

λ λ

V
1
–— CHAP
λ λ
7

501