# Tag: physics

### Questions Related to physics

Students in a lab are trying to determine the wavelength of laser light by shining the laser through two narrow slits separated by $9.60$ micrometers toward a screen $4.00$ meters away. The first order bright fringes are $23.0$ centimeters from the center fringe.
What wavelength do the students determine?

1. $680 nm$

2. $552 nm$

3. $883 nm$

4. $167 nm$

5. $8,832 nm$

Correct Option: B
Explanation:

Given : $d = 9.6$ $\mu m = 9.6 \times 10^{-6}$ $m$      $D = 4.00$  $m$       $y _1 = 23$ cm $= 0.23$ m

Distance of first order bright fringe from central fringe, $y _1 = \dfrac{\lambda D}{d}$
$\therefore$   $0.23 = \dfrac{\lambda \times 4.00}{9.6 \times 10^{-6}}$

$\implies \lambda = 0.552 \times 10^{-6}$ m $=552$  $nm$

The colour of light emitted by a LED depends on

1. Its reverse bias

2. The amount of forward current

3. Its forward bias

4. Type of semiconductor material

Correct Option: D
Explanation:

The color of an LED is a function of the material used to make the junction. There are two main flavors used in visible light LED junctions:

Indium gallium nitride (InGaN) is used to make up the blue, white, true green, and UV types.

Aluminum gallium indium phosphide (AlGaInP or AlInGaP) is used to make the red, yellow, and orange types.

The type of material used also has an effect on the rated forward voltage of the LED.

The colour of light emitted by an LED depends on

1. Its reverse bias

2. The amount of forward current

3. Its forward bias

4. Type of semiconductor material

Correct Option: D
Explanation:

The colour of LED depends on the band gap of the semiconductor material used. When there is an electron transition, the light corresponding to that energy is emitted.

Bye surgery is one of the medical procedures in which laser technology has become an important aid. Who, among the following was the first to produce laser in $1960$?

1. Nikolai Basov

2. Charles Towns

3. Theodore Maiman

4. Aleksandr Prochorov

Correct Option: C
Explanation:

Theodore Harold maiman was the first to produce laser in $1960$.

In He-Ne laser, metastable state exists in:

1. He

2. Ne

3. Both (1) & (2)

4. Neither He nor Ne

Correct Option: C

A laser operates at a frequency of $3\times 10^{14} H _z$ and has an aperture of $1cm$. The radii spread of the beam is

1. $10^{-3}$ radian

2. $5\times 10^{-3}$ radian

3. $10^{-4}$ radian

4. $10^{-2}$ radian

Correct Option: C
Explanation:

Due to non ideality in monochromatic nature of a laser, there exists some spread $\theta$,

$\theta =\dfrac { \lambda }{ \pi r } =\dfrac { c }{ \pi fr }$

$\theta={ 10 }^{ -4 } \ radian$

The principal of LASER action involves

1. amplification of particular frequency emitted by the system

2. population inversion

3. stimulated emission

4. All of the above

Correct Option: D
Explanation:

Laser action involves all of the following.
(i) Amplification of particular frequency.
(ii) Population of inversion.
(iii) Stimulated emission.

Wavelength of a laser beam can be used as a standard of:

1. time

2. temperature

3. angle

4. length

Correct Option: D
Explanation:

Wavelength of a laser beam can be used as a standard of  length because wavelength is considered as the measure of length of the wave.

State whether true or false :
A bulb is used in place of LED to detect weak currents.
1. True

2. False

Correct Option: B
Explanation:

A bulb is cannot be used in place of LED to detect weak currents because at weak current supply bulb cannot glow. Bulb requires specific minimum current to glow. but LED can glow at weak currents at low intensity hence Led is uesd to detect weak currents.

LED glows even when a ______ electric current passes through it. Fill in the blank.

1. weak

2. strong

3. can't predicted

4. none of the  above

Correct Option: A
Explanation:

Principle of LED is the reverse of principle of photo electric effect.

hence even when a weak electric current passes through a circuit respective number of some light photons releases from the LED.
Hence LED glows but with low intensity.