Tag: ray optics

Questions Related to ray optics

If the angle of elevation of sun increases from ${0}^{o}$ to ${90}^{o}$ then what will be the change in length of shadow of tower?

physics reflection of light and shadow beam of light ray and beam ray optics

  1. No change in length of shadow

  2. Length of shadow increases

  3. Length of shadow decreases

  4. Length of shadow will be zero

Show answer
Correct Option: C,D
Explanation:

Length of shadow decreases and will be zero.
"Angle of elevation" is the angle between the thing being referenced and the horizontal. So, when the sun rises the angle of elevation increases and your shadow becomes shorter. When the sun is directly overhead, you don't have a shadow and the angle of elevation is 90, which is the greatest angle. So, the closer to midday, the shorter the shadow and the greater the angle of elevation.

In a room lighted by an electric bulb, it is found that the shadow of the ceiling fan hung in the centre is falling on a wall opposite to the door. What can you say about the position of the bulb? 

physics reflection of light and shadow beam of light ray and beam ray optics

  1. On the wall having the door

  2. On the wall facing the door

  3. On the wall on your right as you enter the room

  4. On the wall on your left as you enter the room

Show answer
Correct Option: A
Explanation:

Answer is A.

When we put any object in between the light source it forms a shadow of that object. The closer the object is to the source of the light, the more light it blocks out, so its shadow is bigger. But if the object is further away, it does not block out much light, and so the shadow is smaller.
Therefore, for the shadow of the ceiling fan to be formed on a wall opposite to the door, the electric bulb must be positioned on the wall having the door.

Which of the following statement is true?

physics reflection of light and shadow beam of light ray and beam ray optics

  1. All light is electromagnetic wave

  2. Electromagnetic energy is created only by heat

  3. Matter emits a single, unique photon when it is heated

  4. All of these

Show answer
Correct Option: A
Explanation:

Option A $\rightarrow $ All light is electromagnetic wave. This option is correct as EM light does not need any medium to travel like EM wave.

Option B $\rightarrow $ Electromagnetic energy created only by heat.
                    This option is false.
Electromagnetic energy can be created in any case of accelerated charge.
Option C $\rightarrow $ When matter is heated many photos are ejected.
                     So this option is false.