Explain the formation of stationary waves in stretched strings and hence deduce the laws of transverse waves in stretched strings. A wire length of 1 m and mass 20 g is stretched with a force of 800 N. Find its fundamental frequency.
Answers
t is given that the energy of the electron beam used to bombard gaseous hydrogen at room temperature is
12.5 eV. Also, the energy of the gaseous hydrogen in its ground state at room temperature is 13.6 eV.
When gaseous hydrogen is bombarded with an electron beam, the energy of the gaseous hydrogen
becomes 13.6 + 12.5 eV i.e., 1.1 eV.
Orbital energy is related to orbit level (n)as:
Forn= 3,
This energy is approximately equal to the energy of gaseous hydrogen. It can be concluded that the
electron has jumped fromn= 1 ton= 3 level.
During its de-excitation, the electrons can jump fromn= 3 ton= 1 directly, which forms a line of the Lyman
series of the hydrogen spectrum.
We have the relation for wave number for Lyman series as:
Where,
R = Rydberg constant = 1.097 × 10 m
λ=Wavelength of radiation emitted by the transition of the electron
Forn= 3, we can obtainλas:
If the electron jumps fromn= 2 ton= 1, then the wavelength of the radiation is given as:
If the transition takes place from n = 3 to n = 2, then the wavelength of the radiation is given as:
This radiation corresponds to the Balmer series of the hydrogen spectrum.
Hence, in Lyman series, two wavelengths i.e., 102.5 nm and 121.5 nm are emitted. And in the Balmer series,
one wavelength i.e., 656.33 nm is emitted.
Physics Syllabus
General:Units and dimensions, dimensional analysis; least count, signicant
gures;
Methods of
measurement and error analysis for physical quantities pertaining to the following experiments:
Experiments based on using Vernier calipers and screw gauge (micrometer), Determination of g using
simple pendulum, Young's modulus by Searle's method, Specic
heat of a liquid using calorimeter, focal
length of a concave mirror and a convex lens using u-v method, Speed of sound using resonance column,
Verication
of Ohm's law using voltmeter and ammeter, and specic
resistance of the material of a wire
using meter bridge and post oce
box.
Mechanics:Kinematics in one and two dimensions (Cartesian coordinates only), projectiles; Uniform
Circular motion; Relative velocity.
Newton's laws of motion; Inertial and uniformly accelerated frames of reference; Static and dynamic
friction; Kinetic and potential energy; Work and power; Conservation of linear momentum and mechanical
energy.
Systems of particles; Centre of mass and its motion; Impulse; Elastic and inelastic collisions.
Law of gravitation; Gravitational potential and eld;
Acceleration due to gravity; Motion of planets and
satellites in circular orbits; Escape velocity.
Rigid body, moment of inertia, parallel and perpendicular axes theorems, moment of inertia of uniform
bodies with simple geometrical shapes; Angular momentum; Torque; Conservation of angular momentum;
Dynamics of rigid bodies with xed
axis of rotation; Rolling without slipping of rings, cylinders and spheres;
Equilibrium of rigid bodies; Collision of point masses with rigid bodies.
Linear and angular simple harmonic motions.
Hooke's law, Young's modulus.
Pressure in a uid;
Pascal's law; Buoyancy; Surface energy and surface tension, capillary rise; Viscosity
(Poiseuille's equation excluded), Stoke's law; Terminal velocity, Streamline ow,
equation of continuity,
Bernoulli's theorem and its applications.
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