Question
Explain the working of LED.
✓
Answer
Working of LED:
- When the LED is forward biased, electrons from the semiconductor's conduction band recombine with holes from the valence band releasing sufficient energy to produce photons that emit monochromatic light.
- Because of the thin layer, a reasonable number of these photons can leave the junction and emit coloured light.
- The amount of light output is directly proportional to the forward current. Thus, the higher the forward current, the higher is the light output.
- The given figure schematically shows the emission of light when the electron-hole pair combines.
Working of LED
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
Show that even as well as odd harmonics are present as overtones in the case of an air column vibrating in a pipe open at both the ends.
Explain, on the basis of kinetic theory, how the pressure of gas changes if its volume is reduced at constant temperature.
In a single-slit diffraction pattern, the distance between the first minimum on the right and the first minimum on the left is $5.2 \ mm$. The screen on which the pattern is displayed is $80 \ cm$ from the slit and the wavelength of light is $5460 \mathring A $. Calculate the slit width.
→Determine the change in wavelength of light during its passage from air to glass. If the refractive index of glass with respect to air is 1.5 and the frequency of light is \(3.5 \times 10^{14} Hz\), find the wave number of light in glass. [Velocity of light in air, \(c=3 \times 10^8 m / s\) ]
The equation of motion of a particle executing SHM is $x = a \sin \left(\frac{\pi}{6} t\right)+ b \cos \left(\frac{\pi}{6} t\right)$, where a $=3 cm$ and $b =4 cm$. Express this equation in the form $x = A \sin \left(\frac{\pi}{6} t+\phi\right)$. Hence, find $A$ and $\varphi$.
→ A metal sphere cools at the rate of \(4^{\circ} C / min\). when its temperature is \(50^{\circ} C\). Find its rate of cooling at \(45^{\circ} C\) if the temperature of surrounding is \(25^{\circ} C\).
Two capacitors of capacities C1 and C2 are joined in series and this combination is joined in parallel with a capacitor of capacity C3. Show that the capacity of the system is C = $\frac{C_{1}\left(C_{2}+C_{3}\right)}{C_{2}}$
→What is an isothermal process? Obtain an expression for work done by a gas in an isothermal process.
Explain the term capacitive reactance. State its unit and dimensions.
Why is the base of a transistor made thin and is lightly doped?