Explanation

Lasers operate on the principle of stimulated emission, proposed by Einstein.

In stimulated emission, an incoming photon stimulates an excited atom to drop to a lower energy level, releasing a new photon.

This new photon has:

• Same energy
• Same wavelength
• Same polarization
• Same phase and direction
• as the photon that stimulated it.

Because of this process, all photons in a laser beam are coherent, monochromatic, and travel in the same direction — a unique property of laser light.

Explanation

Heat is a form of energy.

SI unit of heat = joule (J)

Work

SI unit = joule (J)

 Same as heat

Explanation

 When a forward bias is applied to a p-n junction:

The potential barrier decreases.

Electrons from the n-side move toward the p-side.

These electrons are minority carriers on the p-side.

As a result, the concentration of electrons on the p-side increases, but only slightly, since it's still a small number compared to the holes (which are majority carriers on the p-side).

Explanation

The stopping potential is the voltage applied to the electrodes in a photoelectric effect experiment that just prevents the most energetic electrons from reaching the anode.

Since the kinetic energy of the ejected electrons is directly proportional to the frequency of the incident light (above the threshold frequency), a higher frequency light will result in more energetic electrons.

Therefore, the stopping potential, which is the voltage needed to completely stop these most energetic electrons, is also directly proportional to their energy. 

Explanation

The electromagnetic spectrum in order of increasing frequency (and energy) is:

1. Radio waves (lowest frequency)

2. Infrared (i)

3. Visible light (v)

4. Ultraviolet (u)

5. X-rays (x) (highest frequency among these)

So, the correct sequence from lowest to highest frequency is:
radio (r) < infrared (i) < visible (v) < ultraviolet (u) < x-rays (x)

Explanation

We are told:

• A copper penny is heated to 100 °C.

• Its diameter increases by 0.17%.

• We are to find the percentage increase in the area of one of its circular faces.

Let’s denote:

• Original diameter: $D$
  

• Increased diameter: $D' = D + Delta D = D (1 + 0.0017)$

• Area of a circle: $\mathrm{<br>}$

• New area:

  A′=π(D′)^2​/4=(D(1+0.0017))^2/4π​=A⋅(1+0.0017)^2

Use binomial expansion (for small x):

(1+x)^2≈1+2xwhen x is small

Here, $x=0.0017$, so:

(1+0.0017)^2≈1+2(0.0017)=1+0.0034=1.0034

Thus, the area increases by:

0.34%​

Explanation

The unit cell with the highest symmetry is cubic. 

Among all crystal systems, the cubic unit cell has the highest symmetry because:

• All sides are equal: $a=b=c$

• All angles are right angles α=β=γ=90∘

• It has multiple axes of symmetry and mirror planes

This high degree of symmetry leads to highly uniform and isotropic properties.

Explanation

In an oscillating LC circuit, the maximum energy stored in the capacitor during one cycle is equal to the total stored energy (U) in the circuit.

This is because the total energy oscillates between the capacitor and the inductor, with the total energy remaining constant in an ideal, lossless LC circuit.

Explanation

 The Hall effect is a phenomenon where a voltage develops across a conductor perpendicular to both the applied current and magnetic field.

This voltage is proportional to the magnetic field strength, the current, and the carrier concentration in the conductor.

By measuring this Hall voltage, scientists can determine the concentration of charge carriers (electrons or holes) in a material. 

Explanation

We are given:

• $A=B\cdot C$

• Dimensions:

  • [A]=L/M​

  • [C]=L/T​

We want to find $[B]$.

Step 1: Solve for
$\mathrm{<br>}$B:

B=A/C​

Step 2: Plug in dimensions:

$$<br>$$[C]​

=L​/M/L/T

​​=L​/M​⋅T/L​=T/M​