Class 12th

Class 12th Electromagnetic Waves

Contributor-Level 10

Velocity of bird = v
Velocity w.r.t. observer in water = (4/3)v; 12 = 4 + (3/4)v ⇒ v = 6 cm/s

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

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Class 12th Physics Wave Optics

Contributor-Level 10

s? = -? + k? ∴ s? = (-? +k? )/√2

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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 $(i n μ m) .$

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Contributor-Level 10

$7 * \frac{D λ}{d} = \frac{(μ_{1} - μ_{2}) t . D}{d}$

t = 9.1 $μ m$

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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.

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Contributor-Level 10

Energy of products = 939 + 940 = 1879
ΔE + E_reactions – E_productor = 1877 – 1879 = -2MeV.
Hence it must capture a γ - ray photon of energy 2MeV.

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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.

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Contributor-Level 10

X? = X? ⇒ ωL = R ⇒ 2 * 3.14 * 50 * L = 20 ⇒ L = 63.7mH

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

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Class 12th Dual Nature of Radiation and Matter

Contributor-Level 10

$5 * 1 0^{3} I_{1} = 60$

$\Rightarrow I_{1} = \frac{60}{5 * 1 0^{3}} = 12 m A$

Potential difference across

$10 k Ω = 240 - 60 = 180 V$

$I_{2} = I_{3} - I_{1} = 6 m A$

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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: $(h c = 1240 e V . n m)$

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Raj Pandey

Contributor-Level 9

Photon energy $\frac{}{} \frac{}{}^{}^{}$ $= \frac{h c}{λ} = \frac{1240 e V . n m}{500 n m} = 2.48 e V = 2.48 * 1.6 * 10^{- 19} J = 4 * 10^{- 19} J$

No. of photons emitted per sec $= \frac{power}{photon Energy} = \frac{100}{4 * 10^{- 19}} s^{- 1} = 2.5 * 10^{20} s^{- 1}$

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Class 12th Physics Wave Optics

The truth table for the circuit given in the figure is :

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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:

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Contributor-Level 10

n (7800) = (n + 1) 5200

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Calculate the value of output voltage V₀ (in V) if the Si diode and Ge diode conduct at 0.7V and 0.3V respectively as shown in figure.

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