Intensity

Q.

Which of these light sources will have a cylindrical wave front?

1. Point source

2. Plane source

3. Spherical source

4. Infinite Line source

Q. Energy from a point source spreads out isotropically in all directions.

1. False
2. True

Q.

Which of these light sources will have a cylindrical wave front?

1. Point source

2. Infinite Line source

3. Plane source

4. Spherical source

Q.

Consider the earlier problem where we had a point source radiating energy at the rate of 10 Joules per second, or 10 Watts. What can you say about the intensities $I_{1}and{I}_2$ at two points on spheres of radii and $r_{1}and{r}_2$ respectively, centered at the source?

1. $I_1=I_2$

2. $I_1{r}_1=I_2{r}_2$

3. $I_1{r}_2^2=I_2{r}_1^2$

4. $I_1{r}_1^2=I_2{r}_2^2$

Q.

A bulb of power 100 W that radiates light isotropically(equally in all directions) has dimensions so small compared to the distances in question that the source can be assumed to be a point source.

Find the intensity 10 m away from it?

1. $\frac{1}{4\pi }W/m^2$

2. $\frac{1}{\pi }W/m^2$

3. $\frac{2}{\pi }W/m^2$

4. $Noneofthese$

Q.

A Light source that radiates 10 Joules of energy per second is kept at the centre of a hemisphere. How much energy will the hemisphere receive?

Energy (in Joules) =

Q.

Intensity is:

1. Energy density in a given volume

2. Power density in a given volume

3. Energy per unit area

4. Power per unit area