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Multiple choice physics kirchhoff's law circuit problems kirchoff's law and problems on it equivalent resistance in series and parallel connection

The Kirchhoff's first law $(\displaystyle\sum i=0)$ and second law $\left(\displaystyle \sum iR=\displaystyle\sum E\right)$, where the symbols have their usual meanings, are respectively based on

  1. Conservation of charge, conservation of energy

  2. Conservation of charge, conservation of momentum

  3. Conservation of energy, conservation of charge

  4. Conservation of momentum, conservation of charge
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
$\sum i=0$  (Conservation of charge).
Charge can neither be created or destroyed.
$iR=\sum E$ (Conservation of energy).
Total potential around a loop$=0$ or
Drop in Potential energy=Energy dissipated.
Multiple choice physics kirchhoff's law circuit problems kirchoff's law and problems on it equivalent resistance in series and parallel connection

"A good absorber of a given wavelength of radiation is also a good emitter of that wavelength." This is a statement of:

  1. Stefan-Boltzmann's law

  2. Wien's Law

  3. Kirchoff's Law

  4. The First Law of Thermodynamics
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Kirchhoff's Law of radiation states that for an arbitrary body emitting and absorbing thermal radiation in thermodynamic equilibrium, the emissivity is equal to the absorptivity.

Multiple choice conditions for a light ray to pass undeviated refraction of light at plane surfaces physics

A 5 cm thick glass slab is silvered at one of the surface to form a plane mirror. A point object is placed at a distance of $20cm $ from the unsilvered face. The image distance from the unsilvered face will be [R.I. of glass =1.5]

  1. 26.67cm

  2. $\frac {70}{3}$

  3. 20cm

  4. 25cm
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The object is at 20 cm from the unsilvered face. The light travels through 5 cm of glass (mu=1.5) to reach the mirror. The apparent distance of the object from the mirror is 5/1.5 + 20 = 3.33 + 20 = 23.33 cm. The mirror forms an image at 23.33 cm behind the mirror. The light then travels back through the glass, where the image appears at an apparent distance of 23.33 * 1.5 = 35 cm from the mirror surface. The total distance from the unsilvered face is 35 + 5 = 40 cm? Wait, recalculate: The mirror is at depth 5 cm. Object is at 20 cm from surface. Distance to mirror = 20 + 5/1.5 = 20 + 3.33 = 23.33. Image is at 23.33 behind mirror. Total distance from surface = 23.33 + 5/1.5 = 23.33 + 3.33 = 26.66 cm.

Multiple choice conditions for a light ray to pass undeviated refraction of light at plane surfaces physics

Light starting from a medium of refractive
index $  \mu  $ undergoes refraction into a medium of index $  \mu  $. If I and r stand for angle of incidence are refraction respectively :

  1. $

    \frac{\sin i}{\sin r}=\frac{\mu}{\mu^{\prime}}

    $

  2. $

    \frac{\sin i}{\sin r}=\frac{\mu^{\prime}}{\mu}

    $

  3. $

    \frac{\cos i}{\cos r}=\frac{\mu^{\prime}}{\mu}

    $

  4. $

    \frac{\sin i}{\sin r}=1 / \mu \mu^{\prime}

    $
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice conditions for a light ray to pass undeviated refraction of light at plane surfaces physics

When a light ray is refracted from one medium into another the wavelength change from $4500{ A }^{ 0 }$ to $3000{ A }^{ 0 }$ the critial angle for a ray from second medium to first medium is 

  1. ${ sin }^{ -1 }\left( \dfrac { 2 }{ 3 } \right) $

  2. ${ cos }^{ -1 }\left( \dfrac { 2 }{ 3 } \right) $

  3. ${ tan }^{ -1 }\left( \dfrac { 3 }{ 2 } \right) $

  4. ${ tan }^{ -1 }\left( \dfrac { 2 }{ \sqrt { 5 } } \right) $
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Refractive index mu = lambda1 / lambda2 = 4500 / 3000 = 1.5 = 3/2. The critical angle C is given by sin(C) = 1 / mu = 1 / 1.5 = 2/3. Thus, C = sin^-1(2/3).

Multiple choice conditions for a light ray to pass undeviated refraction of light at plane surfaces physics

Which of the following statements is false?

  1. A plane mirror produce a magnification of +1

  2. Focal length of a plane mirror is infinite

  3. For man of height h, to see his own complete image , a mirror of height at least equal to  h is required

  4. For a ray of light, incidenting normally on a plane mirror, the angle of reflection is $ 180^0 $
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

To see a full image in a plane mirror, the mirror height must be at least half the person's height (h/2), not equal to h. Thus, statement C is false.

Multiple choice conditions for a light ray to pass undeviated refraction of light at plane surfaces physics

A wave has velocity $u$ in medium $P$ and velocity $2u$ in medium $Q$. If the wave is incident in medium $P$ at an angle of $30^\circ$ then the angle of refraction will be

  1. $30^\circ$

  2. $45^\circ$

  3. $60^\circ$

  4. $90^\circ$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Using Snell's Law: sin(i) / sin(r) = v1 / v2. Given i = 30 degrees, v1 = u, v2 = 2u. sin(30) / sin(r) = u / 2u = 1/2. sin(r) = 2 * sin(30) = 2 * 0.5 = 1. Therefore, r = 90 degrees.