Page 253 - Physics Form 5 KSSM_Neat

Generating Photoelectric Current in a CHAPTER 7
Photocell Circuit Glass tube Light
Figure 7.15 shows a photocell circuit consisting of a glass Cathode _ + Anode Quantum Physics
vacuum tube. The semi-cylindrical cathode is coated with a Vacuum
light-sensitive metal and connected to the negative potential.
The anode is a metal rod fixed at the axis of the semi-cylindrical
KEMENTERIAN PENDIDIKAN MALAYSIA
cathode and connected to the positive potential. When the
photocell is illuminated by light, the production of photoelectric _ + mA
current is produced in the circuit. Table 7.5 are two examples of
common photocells. Figure 7.15 A photocell circuit

Table 7.5 Production of photoelectric current by photocells coated with caesium and lithium
Caesium Lithium

Caesium Lithium

Light Light
Cathode Cathode

Anode Anode

µA µA

Work function of caesium, W = 2.14 eV Work function of lithium, W = 2.50 eV

14
Threshold frequency, f = 5.16 × 10 Hz Threshold frequency, f = 6.03 × 10 Hz
14
0 0
Maximum wavelength to produce Maximum wavelength to produce
photoelectric current, l = 579 nm photoelectric current, l = 496 nm
On the whole, the higher the work function, the shorter the maximum wavelength required
to produce photoelectric current. As the light intensity increases, the photoelectric current in the
photocell circuit also increases.

Activity 7.9 ISS ICS

Aim: To observe how photoelectric current is produced in a photocells coated with caesium
through computer animations
Instructions:
1. Carry out this activity in pairs.
SCAN ME
2. Scan the QR code to view a simulation related to the SCAN ME
Animation video
production of photoelectric current in photocells coated on the production
with caesium. of photoelectric
3. Based on the simulation, explain how the photoelectric current current
is produced in a photocell coated with caesium. https://bit.ly/3hriJRr
4. Present your findings.

LS 7.3.5 243