A movie projector forms an image 3.5 m long | vedclass

Name: Exam Paper Generator | JEE NEET Paper Generator | Vedclass
Brand: Vedclass
Rating: 5 (35 reviews)

Question

(B) The illuminance $I$ is defined as the luminous flux per unit area,$I = \frac{\Phi}{A}$.Since the total luminous flux $\Phi$ remains constant (assu

Vedclass · Accepted Answer

$10^4:1$

Vedclass · Answer

(B) The illuminance $I$ is defined as the luminous flux per unit area,$I = \frac{\Phi}{A}$.Since the total luminous flux $\Phi$ remains constant (assuming negligible absorption),the illuminance is inversely proportional to the area of the image,$I \propto \frac{1}{A}$.Since the area $A$ is proportional to the square of the linear dimensions $(A \propto L^2)$,we have $I \propto \frac{1}{L^2}$.Therefore,the ratio of illuminance on the slide $(I_s)$ to the illuminance on the screen $(I_i)$ is given by:$\frac{I_s}{I_i} = \frac{L_i^2}{L_s^2} = \left( \frac{L_i}{L_s} \right)^2$Given $L_i = 3.5 \ m = 3500 \ mm$ and $L_s = 35 \ mm$:$\frac{I_s}{I_i} = \left( \frac{3500 \ mm}{35 \ mm} \right)^2 = (100)^2 = 10000 = 10^4:1$.

$A$ movie projector forms an image $3.5 \ m$ long of an object $35 \ mm$ long. Supposing there is negligible absorption of light by the aperture,what is the ratio of the illuminance on the slide to the illuminance on the screen?

Similar Questions

The figure shows a ray incident at an angle $i = \pi / 3$. The plot shows the variation of $|r - i|$ versus $k = \frac{\mu_1}{\mu_2}$,where $r$ is the angle of refraction. Based on the graph,which of the following statements is correct?

Amount of light entering into the camera depends upon

Assertion : $A$ red object appears dark in the yellow light.
Reason : The red colour is scattered less.

$A$ point source $S$ is placed at a distance of $15 \; cm$ from a converging lens of focal length $10 \; cm$. Where should a concave mirror of focal length $12 \; cm$ be placed so that a real image is formed on the object itself (in $; cm$)?

$A$ point object is placed at a distance of $60\, cm$ from a convex lens of focal length $30\, cm$. If a plane mirror is placed perpendicular to the principal axis of the lens at a distance of $40\, cm$ from it,the final image is formed at a distance of:

Vedclass Test Series

Exam Paper Generator

Online Exam Module