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Physics NCERT Exemplar Solutions Class 12th Chapter Eight

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4 months ago

Physics NCERT Exemplar Solutions Class 12th Chapter Eight Laws of Motion

A mass of 10kg is suspended vertically by a rope of length 5m from the roof. A force of 30 N is applied at the middle point of rope in horizontal direction. The angle made by upper half of the rope with vertical is q = tan^-¹ (x * 10^-¹). The value of x is…………….

(Given, g = 10 m/s²)

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Payal Gupta

Contributor-Level 10

F.B.D. of point 'P'

$T s i n θ = 30$ - (1)

$T c o s θ = 100$ - (2)

$(1) \div (2)$

$t a n θ = \frac{3}{10} \Rightarrow θ = t a n^{- 1} (3 * 1 0^{- 1})$

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Physics NCERT Exemplar Solutions Class 12th Chapter Eight Communication Systems

We do not transmit low frequency signal to long distances because-

(A) The size of the antenna should be comparable to signal wavelength which is unreal

(B) Effective power radiated by a long wavelength baseband signal would be high.

(C) We want to avoid mixing up signals transmitted by different transmitter simultaneously.

(D) Low frequency signal can be sent to log distances by superimposing with a high frequency wave as well.

Therefore, the most suitable options will be

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Physics NCERT Exemplar Solutions Class 12th Chapter Eight Communication Systems

We do not transmit low frequency signal to long distances because-

(A) The size of the antenna should be comparable to signal wavelength which is unreal

(B) Effective power radiated by a long wavelength baseband signal would be high.

(C) We want to avoid mixing up signals transmitted by different transmitter simultaneously.

(D) Low frequency signal can be sent to log distances by superimposing with a high frequency wave as well.

Therefore, the most suitable options will be

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Payal Gupta

Contributor-Level 10

For high wavelength, size of antenna should be high.

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Physics NCERT Exemplar Solutions Class 12th Chapter Eight Semiconductor Electronics

For a transistor to act as a switch, it must be operated in

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Payal Gupta

Contributor-Level 10

For Transistor

to act as a switch → Saturation & cut – off state

to act as an amplifier → Active Region

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Physics NCERT Exemplar Solutions Class 12th Chapter Eight Atoms

Given below are two statements:

Statement I : In hydrogen atom, the frequency of radiation emitted when an electron jumps from lower energy orbit (E₁) to higher energy orbit (E₂), is given as hf = E₁ = E₂

Statement II : The jumping of electron from higher energy orbit (E₂) to lower energy orbit (E₁) is associated with frequency of radiation given as f = (E₂ – E₁) / h

This condition is Bohr's frequency condition.

In the light of the above statements, choose the correct answer from the options given below:

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Payal Gupta

Contributor-Level 10

$E_{2} > E_{1}$

For statement 1

hf = E₁ - E₂

Since, E₂ > E₁

So, it should be

hf = E₂ – E₁

Therefore statement 1 is wrong

For statement 2

For the jumping of electron from higher energy orbit

(E₂) to lower energy orbit (E₁)

hf = E₂ – E₁

$f = \frac{E_{2} - E_{1}}{h}$

Statement (2) is correct

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Physics NCERT Exemplar Solutions Class 12th Chapter Eight Wave Optics

If a wave gets refracted into a denser medium, then which of the following is true?

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Payal Gupta

Contributor-Level 10

$μ_{2} > μ_{1}$

$\frac{μ_{2}}{μ_{1}} > 1$

$μ_{2} = \frac{c}{v_{2}}, μ_{1} = \frac{c}{v_{1}}$

$\frac{μ_{2}}{μ_{1}} = \frac{v_{1}}{v_{2}} > 1 \Rightarrow v_{1} > v_{2}$

Frequency remains constant while refraction since energy is constant

$υ = \frac{v}{λ}$

$λ α v$

$λ_{1} > λ_{2}$

$λ \to$ decreases

wavelength and speed decreases but frequency remains constant

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Physics NCERT Exemplar Solutions Class 12th Chapter Eight Wave Optics

If a wave gets refracted into a denser medium, then which of the following is true?

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Physics NCERT Exemplar Solutions Class 12th Chapter Eight Ray Optics and Optical Instruments

A convex lens has power P. It is cut into two halves along its principal axis. Further one piece (out of the two halves) is cut into two halves perpendicular to the principal axis (as shown in figures). Choose the incorrect option for the reported pieces.

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Payal Gupta

Contributor-Level 10

$R_{1} = R$

$R_{2} = - R$

$P = \frac{1}{f} = (μ - 1) (\frac{1}{R_{1}} - \frac{1}{R_{2}})$

$P = \frac{1}{f} = (μ - 1) (\frac{1}{R} - (\frac{- 1}{R}))$

P = \frac{(μ - 1) 2}{R}

L₂

R₁ = R

$R_{2} = \infty$

$R_{1} = \infty$

R₂ = -R

Power of $L_{1} = \frac{1}{f''} = (μ - 1) (\frac{1}{R_{1}} - \frac{1}{R_{2}})$

Power of $L_{1} = \frac{(μ - 1) * 2}{R} = P$

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Physics NCERT Exemplar Solutions Class 12th Chapter Eight Electromagnetic Waves

Given below are two statements:

Statement I : A time varying electric field is a source of changing magnetic field and vice-versa. Thus a disturbance in electric or magnetic field creates EM waves.

Statement II : In a material medium, the EM wave travels with speed v = $\frac{1}{\sqrt[]{μ_{0} \in_{0}}} .$ In the light of the above statements, choose the correct answer for the options given below

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Payal Gupta

Contributor-Level 10

Statement 1 is true

Speed of EM ware in vaccum is given by,

$C = \frac{1}{\sqrt[]{μ_{0} \in_{0}}}$

Speed of EM wave in a material medium

$v = \frac{1}{\sqrt[]{u_{r} μ_{0} \in_{r} \in_{0}}}$

So, statement (2) is false.

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Physics NCERT Exemplar Solutions Class 12th Chapter Eight Alternating Current

If L, C and R are the self inductance, capacitance and resistance respectively, which of the following does not have the dimension of time?

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Payal Gupta

Contributor-Level 10

Dimension

RC → [T]

$\frac{L}{R} \to [T]$

$\sqrt[]{L c} \to [T]$

$\frac{L}{C} \to$ dimensionless

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