Download App

JUNE 2024 — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsJUNE 20243 Marks
Question
The work function of caesium is 2.14 eV . Find
(a) The threshold frequency for caesium.
(b) The wavelength of incident light if photocurrent is brought to zero by a stopping potential of $0.60 V .\left( h =6.625 \times 10^{-34} Js \right)$
✓

Answer


$
\begin{array}{c}
\varphi_0=2.14 eV \\
V_0=0.60 V \\
v_0=? \\
\lambda=?
\end{array}
$
→ (a)The cut off or threshold frequency
$
\begin{array}{l}
\varphi_0=h v_0 \\
\therefore v_0=\frac{\phi_0}{h} \\
=\frac{2.14 \times 1.6 \times 10^{-19}}{6.625 \times 10^{-34}} \\
v_0=0.5163 \times 10^{15} Hz \\
v_0=5.16 \times 10^{14} Hz
\end{array}
$
→ (b) Einstein's photoelectric equation is
$\begin{array}{l} K _{\max }=h v-\varphi_0 \\ \text { but } K _{\max }=e V_0 \\ \therefore e V_0=\frac{h c}{\lambda}-\varphi_0( C =v \lambda) \\ \therefore \frac{h c}{\lambda}=e V_0+\varphi_0 \\ \therefore \frac{h c}{\lambda}=\left(1.6 \times 10^{-19} \times 0.60\right)+\left(2.14 \times 1.6 \times 10^{-19}\right) \\ \therefore \frac{h c}{\lambda}=1.6 \times 10^{-19}(0.60+2.14)\end{array}$
$\therefore \frac{h c}{\lambda}=4.384 \times 10^{-19}$
$\therefore \lambda=\frac{6.625 \times 10^{-34} \times 3 \times 10^8}{4.384 \times 10^{-19}}$
$\begin{array}{l}\therefore \lambda=4.54 \times 10^{-7} m \\ =454 \times 10^{-9} m \\ \lambda=454 nm\end{array}$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "3 Marks Question" from JUNE 2024→JUNE 2024 — all question types→Physics STD 12 Science question papers→Gujarat Board STD 12 Science question papers→Gujarat Board question paper generator→

Similar questions

2g of hydrogen is sealed in a vessel of volume 0.02m3 and is maintained at 300K. Calculate the pressure in the vessel.
→
Estimate the proportion of boron impurity whieh will increase the conductivity of a pure silicon sample by a factor of 100. Assume that each boron atom creates a hole and the concentration of holes in pure silicon at the same temperature is 7 × 1015 holes per cubic metre. Density of silicon is 5 × 1021 atoms per cubic metre.
→
Figures 2.8 (a) and (b) show the field lines of a positive and negative point charge respectively.
Image
(a) Give the signs of the potential difference $V_{ P }-V_{ Q } ; V_{ B }-V_{ A }$.
(b) Give the sign of the potential energy difference of a small negative charge between the points $O$ and $P ; A$ and $B$.
(c) Give the sign of the work done by the field in moving a small positive charge from $Q$ to $P$.
(d) Give the sign of the work done by the external agency in moving a small negative charge from $B$ to $A$.
(e) Does the kinetic energy of a small negative charge increase or decrease in going from $B$ to $A$ ?
→
The work function for a certain metal is 4.2 eV. Will this metal give photoelectric emission for incident radiation of wavelength 330 nm?
→
A candle flame 1.6cm high is imaged in a ball bearing of diameter 0.4cm. If the ball bearing is 20cm away from the flame, find the location and the height of the image.
→
A 3cm tall object is placed at a distance of 7.5cm from a convex mirror of focal length 6cm. Find the location, size and nature of the image.
→
Find the equivalent capacitance of the network shown in the figure, when each capacitor is of $1\mu\text{F}$. When the ends X and Y are connected to a 6 V battery, find out (i) The charge and (ii) The energy stored in the network.
→
Two blocks of masses m1 and m2 are connected by a spring of spring constant k. The block of mass m2 is given a sharp impulse so that it acquires a velocity v0 towards right. Find
  1. The velocity of the centre of mass.
  2. The maximum elongation that the spring will suffer.
​​​​​​​
→
How does Maxwell modify Ampere's circuital law? Explain.
→
Is the motion of a charge across junction momentum conserving? Why or why not?
→