Class 12th

A capacitor of capacitance 3µF is charged to a potential difference of 12V. Another identical capacitor, initially uncharged is filled with a dielectric having dielectric constant K and it is connected to the charged capacitor. The final common potential difference across both capacitors is found to be 2V. Find the value of k.

In a young's double slit experiment with monochromatic light, fringes are obtained on a screen placed at some distance from the slits. If the screen is moved 8 cm towards the slits, the change in fringe width is 4 * 10^-5 m. If the separation between the slits is 1 mm, find the wavelength of light used (in nm ).

A fish moving up in water (μ = 4/3) with a speed of 4 cm/s observes a bird coming directly towards itself with a speed of 12 cm/s. Find the actual speed of the bird with respect to a stationary observer on the ground.

An electromagnetic wave is represented by the electric field
E⃗ = E₀n̂[ωt + (y − z)]
The direction of propagation of the wave, ŝ is:

A monochromatic light of wavelength 6500 Å is used in YDSE. Now both slits are covered by two thin slab of refractive index 3.2 and 2.7 respectively. By doing so central bright fringe shifts to original 7^th bright fringe. If both slabs have same thickness then thickness of slab is $\left(in\mu m\right).$  

The rest mass of the deuteron, proton and neutron is equivalent to energy of 1877MeV, 939MeV, 940MeV respectively. A deuteron may disintegrate to a proton and neutron if it.

An inductor and a resistor are connected to an ac supply of 120 V, 50 Hz. The resistance of the resistor is 20Ω. If the voltages leads the current by a phase difference of 45°, find the inductance of the inductor.

Write the value of current i₃ (in mA) in the circuit shown in the figure.

A source of light emits monochromatic visible light of wavelength 500 nm. The source emits light of power 100W. The number of photons emitted per sec of the visible light of the given wavelength is: $(\mathrm{h}\mathrm{c}=1240\mathrm{e}\mathrm{V}.\mathrm{n}\mathrm{m})$

In Young's double slit experiment, the wavelength of red light is 7800 Å and that of blue light is 5200 Å. minimum value of n for which n^th bright band due to red light coincides with (n + 1)^th bright band due to blue light, is: