Question:
A certain metallic surface is illuminated by monochromatic radiation of wavelength $\lambda$. The stopping potential for photoelectric current for this radiation is $3 \mathrm{~V}_{0}$. If the same surface is illuminated with a radiation of wavelength $2 \lambda$, the stopping potential is $\mathrm{V}_{0}$. The threshold wavelength of this surface for photoelectric effect is_________$\lambda$.
Solution:
$\mathrm{KE}=\frac{\mathrm{hc}}{\lambda}-\phi \mathrm{hc}$
$\mathrm{e}\left(3 \mathrm{~V}_{0}\right)=\frac{\mathrm{hc}}{\lambda_{0}}-\phi$ ..........(i)
$\mathrm{eV}_{0}=\frac{\mathrm{hc}}{2 \lambda_{0}}-\phi$ ..............(ii)
Using (i) & (ii)
$\phi=\frac{h c}{4 \lambda_{0}}=\frac{h c}{\lambda_{t}}$
$\lambda_{t}=4 \lambda_{0}$
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- JEE Main
- Exam Pattern
- Previous Year Papers
- PYQ Chapterwise
- Physics
- Kinematics 1D
- Kinemetics 2D
- Friction
- Work, Power, Energy
- Centre of Mass and Collision
- Rotational Dynamics
- Gravitation
- Calorimetry
- Elasticity
- Thermal Expansion
- Heat Transfer
- Kinetic Theory of Gases
- Thermodynamics
- Simple Harmonic Motion
- Wave on String
- Sound waves
- Fluid Mechanics
- Electrostatics
- Current Electricity
- Capacitor
- Magnetism and Matter
- Electromagnetic Induction
- Atomic Structure
- Dual Nature of Matter
- Nuclear Physics
- Radioactivity
- Semiconductors
- Communication System
- Error in Measurement & instruments
- Alternating Current
- Electromagnetic Waves
- Wave Optics
- X-Rays
- All Subjects
- Physics
- Motion in a Plane
- Law of Motion
- Work, Energy and Power
- Systems of Particles and Rotational Motion
- Gravitation
- Mechanical Properties of Solids
- Mechanical Properties of Fluids
- Thermal Properties of matter
- Thermodynamics
- Kinetic Theory
- Oscillations
- Waves
- Electric Charge and Fields
- Electrostatic Potential and Capacitance
- Current Electricity
- Thermoelectric Effects of Electric Current
- Heating Effects of Electric Current
- Moving Charges and Magnetism
- Magnetism and Matter
- Electromagnetic Induction
- Alternating Current
- Electromagnetic Wave
- Ray Optics and Optical Instruments
- Wave Optics
- Dual Nature of Radiation and Matter
- Atoms
- Nuclei
- Semiconductor Electronics: Materials, Devices and Simple Circuits.
- Chemical Effects of Electric Current,
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