Here is your answer
b) 
REASON :
We know that
Velocity= Frequency× Wavelength
So,
Frequency= Velocity/wavelength
Here,
V= 3× 10^8 m/s
Wavelength= 2×10^-3 m
Hence,
Frequency= 3×10^8/2×10^-3
= 3/2 × 10^11
= 1.5× 10^11 Hz
HOPE IT IS USEFUL
Answer:

Explanation:
Given:
- mass of the object on a horizontal surface,

- coefficient of static friction,

- coefficient of kinetic friction,

- horizontal force on the object,

<u>Now the value of limiting frictional force offered by the contact surface tending to have a relative motion under the effect of force:</u>

where:
normal force of reaction acting on the body= weight of the body


As we know that the frictional force acting on the body is always in the opposite direction:
So, the frictional force will not be at its maximum and will be equal in magnitude to the applied external force and hence the body will not move.
so, the frictional force will be:

Gravitational I think would be the answer, Hope this helps!
Answer:
Studies show that eating fewer animal-based products could reduce water use since animal production uses more water than crops do. In addition, reducing the amount of food that's lost or wasted at various points in the food supply chain could feed about 1 billion extra people while simultaneously reducing water use.
Answer:
<h2>66.67 km/hr</h2>
Explanation:
The average velocity of the car can be found by using the formula

d is the distance
t is the time taken
From the question we have

We have the final answer as
<h3>66.67 km/hr</h3>
Hope this helps you