List of top Questions asked in UP Board XII

What is meant by threshold wavelength \( \lambda_0 \) and threshold frequency \( \nu_0 \) in photoelectric effect? On which factors do the saturation current and the value of cut-off voltage depend?
What is the main difference between a cell and a battery? In which conditions do the following combinations of cells become useful and why?
(i) Series combination
(ii) Parallel combination
(iii) Mixed combination
The focal lengths of a convergent and a divergent lens are \( f_1 \) and \( f_2 \) respectively. If the lenses are placed in contact, then in the following conditions of combination, write the nature of the combined lens and also draw the ray diagram: (i) \( f_1>f_2 \)
(ii) \( f_1<f_2 \)
(iii) \( f_1 = f_2 \)
(i) Condition: \( f_1>f_2 \)

On which factors and how do the following depend? 

(i) Internal resistance of cell 
(ii) Resistance of conductor

In a spherical mirror, the distance between the focus point and centre of curvature is \( 20 \, \text{cm} \). Calculate the following and write their names: (i) The distance of pole of mirror from its focal point.
(ii) The distance of pole of mirror from its centre of curvature. \vspace{0.5cm} (i) The distance of pole of mirror from its focal point

Compare the Astronomical Telescope and Compound Microscope on the basis of the following: 

(i) Components
(ii)Magnifying power
Explain with reason whether any one of the above devices can be used as the other device.
(i) Components

Represent the variation of binding energy per nucleon with mass number. On the basis of it, explain the following: (i) Nuclear fission
(ii) Nuclear fusion
(iii) Nuclear energy
The energy of a hydrogen atom in an energy state is \( -3.4 \) electron-volts. For an electron in this energy state, calculate the following: (i) Binding energy
(ii) Ionization potential
(iii) The number of energy states
(iv) The angular momentum
(v) Kinetic energy
(i) Binding Energy
On what factors does the magnetic flux linked with a coil depend? Explain the induced electromotive force on the basis of the following:
(i) Cause
(ii) Magnitude
(iii) Direction
On what principle does the transformer work? State the following conditions for an ideal transformer:
(i) Leakage of magnetic flux
(ii) Resistance of primary coil
(iii) Resistance of secondary coil
(iv)Dissipation of power
Write the relation between SI and MKS units of electric power.
If the resistance of ammeter and milli-ammeter are \( x_1 \) and \( x_2 \) respectively, then:
In nuclear reaction, \( _{7}^{15}N + _{0}^{1}n \rightarrow _{6}^{14}C + P \), what is P?
What is the nature of n-type semiconductor?
In lens maker formula \( \frac{1}{f} = (n-1) \left( \frac{1}{R_1} - \frac{1}{R_2} \right) \), which focal length is used?
What is \( p\text{-}n \) junction rectifier? Draw circuit diagram of (i) half-wave rectifier (HWR) and (ii) full-wave rectifier (FWR). (i) Half-Wave Rectifier (HWR)
When a capacitor of capacity \( C \) is charged with charge \( q \) and potential difference \( V \), the electric field \( E \) and the electrostatic energy \( U \) is obtained between plates of capacitor. If the capacitor is disconnected from the source and a slab of medium having the same thickness and dielectric constant \( k \) is introduced completely between the plates, calculate the new values of the following:
(i)Capacity
(ii) Potential difference
(iii) Charge
(iv) Electric field
(v) Electrostatic potential energy
(i) Capacity
A plane electromagnetic wave is represented by the equation \[ E = 100 \cos(6 \times 10^8 t + 4x) \, \text{volt/metre}. \] Calculate the following:
(i) The refractive index of the medium
(ii) The velocity of electromagnetic wave in the medium
(iii) The expression for magnetic field
A proton, a deuteron and an alpha particle of same velocity enter perpendicularly in an uniform magnetic field of \( 10^5 \) tesla. Calculate the ratio of their time periods of revolution.
The angle of prism is equal to its minimum deviation angle (\( \delta_m \)). In minimum deviation condition, calculate the following: (i) The angle of incidence
(ii) The angle of refraction
(iii) The refractive index of the material of the prism.
Who discovered the photoelectric effect?
If \( \varepsilon_0 \) and \( \mu_0 \) represent permittivity and permeability of free space, then \( \frac{1}{\sqrt{\varepsilon_0 \mu_0}} \) represents which physical quantity?
If wavelength \( \lambda \) represents wave property and momentum \( p \) represents the particle property, then what will the expressions \( \lambda = \frac{h}{p} \) and \( p = \frac{h}{\lambda} \) represent?
How are optical ray and wavefront related with each other?
If the mass defect of a nucleus is \(2 \times 10^{-6}\) kg, then calculate its binding energy in (i) joule and (ii) electron-volt.