Applied Physics
- How do you solve numerical problems on the energy of a particle in a rigid box? In one line Use E_n = n²h²/(8mL²) in SI units for the required level, and use Δ E = E_(n_2) - E_(n_1) with λ = hc/Δ E for transitions betwee... 1
- What is quantum mechanical tunnelling and how can a particle cross a barrier higher than its energy? In one line Quantum tunnelling is the effect in which a particle has a non-zero probability of passing through a potential barrier even when... 1
- What is a qubit and how is it different from a classical bit in quantum computing? In one line A qubit is the basic unit of quantum information that can exist in a superposition of the states |0rangle and |1rangle at the sa... 1
- What is the gradient of a scalar field and what is its physical meaning? In one line The gradient of a scalar field is a vector that points in the direction in which the field increases fastest, and its magnitude... 1
- What is the divergence of a vector field and what does it tell us physically? In one line Divergence of a vector field measures the net outward flow (flux) per unit volume from a point, showing whether the point acts a... 1
- What is the curl of a vector field and what is its physical significance? In one line Curl of a vector field is a vector that measures how much the field circulates or rotates around a point, with direction along t... 1
- What does Gauss's law of electrostatics state and how is its point form obtained? In one line Gauss's law states that the total electric flux through any closed surface equals the net charge enclosed divided by ε₀ ; in poi... 1
- What is Ampere's circuital law and how is it written in differential (point) form? In one line Ampere's circuital law states that the line integral of magnetic field around any closed loop equals μ₀ times the net current pa... 1
- What does Faraday's law of electromagnetic induction state and what is its point form? In one line Faraday's law states that the emf induced in a closed loop equals the negative rate of change of magnetic flux through it; in po... 1
- What is the critical angle and when does total internal reflection of light take place? In one line The critical angle is the angle of incidence in the denser medium for which the refracted ray just grazes the boundary, and for... 1
- How does light propagate through an optical fibre by total internal reflection? In one line An optical fibre guides light because its core has a higher refractive index than its cladding, so light entering within the acc... 1
- What are the acceptance angle and acceptance cone of an optical fibre? In one line The acceptance angle is the maximum angle to the fibre axis at which light can enter the fibre and still be guided by total inte... 1
- What is the numerical aperture of an optical fibre and how is its formula derived? In one line Numerical aperture (NA) is the sine of the acceptance angle (times the index of the outside medium) and measures how much light... 1
- What is the difference between single-mode and multimode optical fibres? In one line A single-mode fibre has a very thin core that lets only one path (mode) of light travel, while a multimode fibre has a thicker c... 1
- How do step-index and graded-index optical fibres differ in structure and light travel? In one line In a step-index fibre the core has one uniform refractive index that drops suddenly at the cladding, while in a graded-index fib... 1
- What is attenuation in an optical fibre and how is the attenuation coefficient calculated? In one line Attenuation is the gradual loss of optical power as light travels along a fibre, and the attenuation coefficient gives this loss... 1
- What factors cause attenuation or signal loss in an optical fibre? In one line Attenuation in fibres is caused mainly by absorption, scattering and bending losses, plus losses at joints and connectors. Expla... 1
- What are the main blocks of a fibre optic communication system and what does each do? In one line A fibre optic communication system converts an electrical signal into light at the transmitter, sends it through an optical fibr... 1
- Why is optical fibre communication better than copper cable communication? In one line Optical fibres carry far more information over longer distances with lower loss and no electrical interference, while being ligh... 1
- What are the conditions for bright and dark fringes in reflected light from a thin film? In one line In reflected light from a thin film, brightness occurs when 2μ tcos r = (2n-1)λ/2 and darkness when 2μ tcos r = nλ . Explained s... 1
- How does interference occur in a thin film of uniform thickness, and what is the path difference? In one line Light reflected from the top and bottom surfaces of a thin film comes from the same wave (division of amplitude), so the two ref... 1
- How are interference fringes formed in a wedge-shaped thin film and what is the fringe width? In one line A wedge-shaped film has thickness increasing steadily from the edge, so each fringe follows a line of constant thickness, giving... 1
- How are Newton's rings formed and why is the central spot dark in reflected light? In one line Newton's rings are concentric circular fringes formed by interference in the air film between a plano-convex lens and a flat gla... 1
- How are Newton's rings used to find the wavelength of monochromatic light? In one line By measuring the diameters of two dark rings that are p rings apart and knowing the lens radius R , the wavelength is found from... 1