UV Light Source: Fixed in position, projecting a beam onto a rotating mirror (Mirror A) mounted on a servo motor.

Mirror A: Starts at 180° and rotates 45° clockwise every 2 seconds until it reaches 0°, then reverses direction, moving counterclockwise back to 180°. This rotation cycle repeats continuously.

Mirror B: Positioned below Mirror A at a fixed 45° angle. Mirror B is mounted on a second servo motor and starts at 90°, initially reflecting light towards Wall 3 (Front Wall). Mirror B rotates 30° clockwise every 3 seconds until it reaches 0°, then reverses direction and rotates counter clockwise back to 180°.

Bioluminescent Walls: Four walls coated with bioluminescent material are arranged around the setup:

a) Wall 1 (Front Wall)

b) Wall 2 (Right Wall)

c) Wall 3 (Back Wall)

d) Wall 4 (Left Wall)

When the UV light beam reflects off both Mirror A and Mirror B, it strikes one of the four walls, causing it to glow.

Challenge: At 14 seconds after the setup starts, which wall will glow when the UV light reflects off both mirrors?

UV Light Source: Fixed in position, projecting a beam at a mirror mounted on a servo motor.

Servo Motor: Starts at 180° and rotates 45° clockwise every 2 seconds until it reaches 0°. Then, it reverses direction, moving counterclockwise back to 180°. This rotation cycle repeats continuously.

Fixed Mirror: Positioned below the rotating mirror at a fixed 45° angle. It reflects the UV light beam towards one of four walls coated with a bioluminescent material. These walls glow when struck by UV light.

Challenge: At 10 seconds after the servo motor starts rotating, which wall will glow when the UV light reflects off the mirrors?

Currently, the LED emits light with an energy gap of 2.2 eV, which corresponds to orange. However, the researchers are adjusting the doping process of the material. By doping the material, they increase the energy gap by 10%. This change in the energy gap will shift the wavelength of the light emitted, thereby changing the colour of the LED light.

The energy gap formula used to calculate the band gap from the wavelength is:

Energy gap (eV) = 1240/Wavelength (nm)​

Question: Identify the correct nameboard sign from the images.

- The colour of the light depends on the wavelength emitted, which is determined by the bandgap energy of the semiconductor.

- Higher bandgap energy produces shorter wavelengths (colours like blue or violet).

- Lower bandgap energy produces longer wavelengths (colours like red or orange).

They begin with an LED that emits green light (530 nm) with a doping concentration of 5 percent. By reducing or increasing the doping concentration, they aim to create new colours:

- When they reduced the doping concentration to 3.5 percent, the colour shifted to Yellow (580 nm), indicating a lower bandgap energy.

- Next, they increased the doping concentration to 6.5 percent, and the colour shifted to Blue (475 nm), indicating a higher bandgap energy.

Here is a reference table of wavelengths and corresponding colours:

(Refer to the image below for the table)

Challenge: If the inventors increase the doping concentration from their starting point by 2 percent, which of the following wavelengths is most likely to be emitted?