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Class 12th Physics Atoms

The wavelength of the photon emitted by a hydrogen atom when an electron makes a transition from n = 2 to n = 1 state is

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Payal Gupta

Contributor-Level 10

Using Bohr's theory :

$λ = \frac{h c}{E_{2} - E_{1}} = \frac{1242 e V - n m}{(- 3.4) - (- 13.6)} = 121.8 n m$

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Class 12th Dual Nature of Radiation and Matter

An electron of mass m_e and a proton of mass m_p = 1836 m_e are moving with the same speed. The ratio of their de Broglie wavelength $\frac{λ_{e l e c t r o n}}{λ_{p r o t o n}}$ will be

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Payal Gupta

Contributor-Level 10

Using de-Broglie equation for wave nature of particle :

$λ = \frac{h c}{m v} \Rightarrow λ α \frac{1}{m}$

$\frac{λ_{e}}{λ_{P}} = \frac{\frac{1}{m_{e}}}{\frac{1}{m_{P}}} = \frac{m_{P}}{m_{e}} = 1836$

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Class 12th Physics Wave Optics

Consider the diffraction pattern obtained from the sunlight incident on a pinhole of diameter $0.1 μ m .$ If the diameter of the pinhole is slightly increased, it will affect the diffraction pattern such that

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Payal Gupta

Contributor-Level 10

Using diffraction formula of circular hole :

$r α \frac{1}{D}$

size will decease.

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5 months ago

Class 12th Physics

If a message signal of frequency 'f_m' is amplitude modulated with a carrier signal of frequency 'f_c' and radiated through an antenna, the wavelength of the corresponding signal in air is

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Payal Gupta

Contributor-Level 10

$λ_{a i r} = \frac{c}{f_{c}}$

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5 months ago

Class 12th Physics Electric Charge and Field

A charge 'q' is placed at one corner of a cube as shown in figure. The flux of electrostatic field $\vec{E}$ through the shaded area is

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Payal Gupta

Contributor-Level 10

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Class 12th Physics Alternating Current

An LCR circuit contains resistance of 110 $Ω$ and a supply of 220 V at 300 rad/s angular frequency. If only capacitance is removed from the circuit, current lags behind the voltage by 45°. If on the other hand, only inductor is removed the current leads by 45° with the applied voltage. The rms current flowing in the circuit will be

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Payal Gupta

Contributor-Level 10

When capacitor is removed

tan 45° = $\frac{X_{L}}{X_{R}} \Rightarrow ω L = R$

When inductor is removed.

$t a n 45 ° = \frac{X_{C}}{X_{R}} \Rightarrow \frac{1}{ω C} = R$

$i_{0} = \frac{V_{0}}{Z} = \frac{V_{0}}{\sqrt[]{R^{2} + {(ω L - \frac{1}{ω C})}^{2}}} = \frac{V_{0}}{R} = \frac{220}{110} = 2 A$

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Class 12th Physics

For extrinsic semiconductors; when doping level is increased

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Payal Gupta

Contributor-Level 10

Fermi level of p-type semiconductors will go downward

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Class 12th Physics

The stopping potential for electrons emitted from a photosensitive surface illuminated by light of wavelength 491 nm is 0.710 V. When the incident wavelength is changed to a new value, the stopping potential is 1.43V. The new wavelength is

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