Science (English Medium) Class 12 - CBSE Question Bank Solutions

Which one of the following electromagnetic radiation has the least wavelength?

Which of the following statements about a series LCR circuit connected to an ac source is correct?

How would the stopping potential for a given photosensitive surface change if the intensity of incident radiation was decreased? Justify your answer.

How would the stopping potential for a given photosensitive surface change if the frequency of the incident radiation were increased? Justify your answer.

Identify the electromagnetic wave whose wavelength range is from about 10^-12 m to about 10^-8 m. Write one use of this.

Identify the electromagnetic wave whose wavelength range is from about 10^-3 m to about 10^-1 m. Write one use of this.

Using Huygens's construction, show how a plane wave is reflected from a surface. Hence verify the law of reflection.

An alternating voltage of 220 V is applied across a device X. A current of 0.22 A flows in the circuit and it lags behind the applied voltage in phase by π/2 radian. When the same voltage is applied across another device Y, the current in the circuit remains the same and it is in phase with the applied voltage.

1. Name the devices X and Y and,
2. Calculate the current flowing in the circuit when the same voltage is applied across the series combination of X and Y.

Choose the correct option related to wavelengths (λ) of different parts of the electromagnetic spectrum.

The figure shows a plot of stopping potential (V₀) versus `1/lambda`, where λ is the wavelength of the radiation causing photoelectric emission from a surface. The slope of the line is equal to ______.

Identify the electromagnetic radiation and write its wavelength range, which is used to kill germs in water purified. Name the two sources of these radiations.

Plot a graph showing the variation of photoelectric current, as a function of anode potential for two light beams having the same frequency but different intensities I₁ and I₂ (I₁ > I₂). Mention its important features.

With the help of a diagram, show how a plane wave is reflected from a surface. Hence, verify the law of reflection.

A metallic plate exposed to white light emits electrons. For which of the following colours of light, the stopping potential will be maximum?

• Assertion (A): For the radiation of a frequency greater than the threshold frequency, the photoelectric current is proportional to the intensity of the radiation.
• Reason (R): Greater the number of energy quanta available, the greater the number of electrons absorbing the energy quanta and the greater the number of electrons coming out of the metal.

Identify the part of the electromagnetic spectrum which:

1. produces the heating effect.
2. is absorbed by the ozone layer in the atmosphere.
3. is used for studying crystal structure.

Write any one method of the production of each of the above radiations.

Draw the phasor diagram for a series LRC circuit connected to an AC source.

When an alternating voltage of 220V is applied across device X, a current of 0.25A flows which lags behind the applied voltage in phase by π/2 radian. If the same voltage is applied across another device Y, the same current flows but now it is in phase with the applied voltage.

1. Name the devices X and Y.
2. Calculate the current flowing in the circuit when the same voltage is applied across the series combination of X and Y.

A series LCR circuit is connected to an ac source. Using the phasor diagram, derive the expression for the impedance of the circuit.

What is the effect of threshold frequency and stopping potential on increasing the frequency of the incident beam of light? Justify your answer.