PH | MCQs

Explanation

The energy of a photon is calculated using the formula E = hf, where:

• h = Planck’s constant
• f = frequency of the photon

This shows that photon energy is directly proportional to its frequency.

Explanation

Given:

• Radius of the circle$r=4$ meters

• Arc length (distance along the circumference), $s=14$ meters

We are to find the displacement, which is the straight-line distance between the starting and ending points of the arc.

Step 1: Find the angle subtended by the arc at the center (θ in radians):

$$theta = frac{s}{r} = frac{14}{4} = 3.5 , text{radians}$$

Step 2: Use the chord length formula to find displacement:

Displacement=2rsin(θ/2​)
=2×4×sin(3.5/2​)=8×sin(1.75)
sin(1.75radians)≈0.983
$$\text{Displacement}\approx 8\times 0.983\approx 7.864\text{meters}$$

Explanation

The law of conservation of energy is based on the principle of Bernoulli's theorem.

Bernoulli's theorem states that in a steady flow of an incompressible, frictionless fluid, the total mechanical energy (sum of potential energy, kinetic energy, and pressure energy) per unit mass of the fluid remains constant along a streamline.

This means that the total energy of the fluid is conserved as long as no external forces are acting on it, such as friction or heat transfer.

Explanation

In Simple Harmonic Motion (S.H.M.), frequency is a constant and does not depend on the particle's position (mean or extreme).

• At the mean position, the velocity is maximum, and the acceleration is zero, but the frequency remains constant throughout the motion.

Explanation

Atto (a) = 10⁻¹⁸

Femto (f) = 10⁻¹⁵

Nano (n) = 10⁻⁹

Peta (P) = 10¹⁵

So, Atto has the smallest (lowest) value.

Explanation

Explanation

Formula:

B=μ0​I/2πr​

Where:

• $mu_0 = 4pi times 10^{-7} , text{T·m/A}$ 

• $I = 5 , text{A}$ (current)

• $r = 2,text{cm} = 0.02,text{m}$

Substituting Values:

$$B = frac{4pi times 10^{-7} , text{T·m/A} times 5 , text{A}}{2 times 3.14 times 0.02, text{m}}$$2×3.14×0.02m​

Let’s calculate step by step:

Numerator:

$$4pi times 10^{-7} times 5 = 20pi times 10^{-7}$$

Denominator:

$$2 times 3.14 times 0.02 = 0.1256$$

Now,

$$B = frac{20pi times 10^{-7}}{0.1256}$$0.1256​

$$approx frac{62.8 times 10^{-7}}{0.1256} approx 5 times 10^{-5} , text{T}$$0.1256 ≈5×10^−5T

Explanation

 Magnetic force is a force that acts on moving charged particles, causing them to change their direction of motion, essentially deflecting them. 

Explanation

Maximum height is reached when vertical velocity becomes zero.  

Using the kinematic equation:  

v² = u² - 2gh, with final v = 0,  

h = (vi² * sin²θ) / 2g.

Explanation

 T = 2π√(L/g)

= 2π√(1/9.8)

≈ 2.006 s