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Show using a proper diagram how unpolarised light can be linearly polarised by reflection from a transparent glass surface.
Concept: Polarisation
If one of two identical slits producing interference in Young’s experiment is covered with glass, so that the light intensity passing through it is reduced to 50%, find the ratio of the maximum and minimum intensity of the fringe in the interference pattern.
Concept: Interference of Light Waves and Young’s Experiment
What kind of fringes do you expect to observe if white light is used instead of monochromatic light?
Concept: Refraction of Monochromatic Light
Using Huygens’ principle, verify the laws of reflection at a plane surface.
Concept: Huygens' Principle
If light of wavelength 412.5 nm is incident on each of the metals given below, which ones will show photoelectric emission and why?
| Metal | Work Function (eV) |
| Na | 1.92 |
| K | 2.15 |
| Ca | 3.20 |
| Mo | 4.17 |
Concept: Photoelectric Effect and Wave Theory of Light
A hydrogen atom initially in the ground level absorbs a photon, which excites it to the n = 4 level. Determine the wavelength and frequency of the photon.
Concept: Energy Levels
State Bohr's postulate to define stable orbits in the hydrogen atom. How does de Broglie's hypothesis explain the stability of these orbits?
Concept: Bohr’s Model for Hydrogen Atom
A radioactive isotope has a half-life of T years. How long will it take the activity to reduce to a) 3.125%, b) 1% of its original value?
Concept: Law of Radioactive Decay
A student wants to use two p-n junction diodes to convert alternating current into direct current. Draw the labelled circuit diagram she would use and explain how it works.
Concept: p-n Junction
Draw a typical input and output characteristics of an n-p-n transistor in CE configuration. Show how these characteristics can be used to determine (a) the input resistance (r1), and (b) current amplification factor (β)
Concept: Transistor and Characteristics of a Transistor
Give three reasons why modulation of a message signal is necessary for long-distance transmission
Concept: Need for Modulation and Demodulation
Show graphically an audio signal, a carrier wave and an amplitude modulated wave
Concept: Need for Modulation and Demodulation
A carrier wave of peak voltage 15 V is used to transmit a message signal. Find the peak voltage of the modulating signal in order to have a modulation index of 60%
Concept: Modulation and Its Necessity
What is biopiracy?
Concept: Ethical Issues
How do you convert the following:
Aniline to phenol
Concept: Methods of Preparation of Phenols
How do you convert the Ethanal to Propanone
Concept: Alcohols, Phenols and Ethers >> Nomenclature
When concentrated sulphuric acid was added to an unknown salt present in a test tube a brown gas (A) was evolved. This gas intensified when copper turnings were added to this test tube. On cooling, the gas (A) changed into a colourless solid (B).
1) Identify (A) and (B).
2) Write the structures of (A) and (B).
3) Why does gas (A) change to solid on cooling?
Concept: P - Block Group 16 Elements >> Sulphuric Acid
Arrange the following in the decreasing order of their reducing character :
HF, HCl, HBr, HI
Concept: Concept of Group 17 Elements
Account for the following:
pKa value of 4-nitrobenzoic acid is lower than that of benzoic acid.
Concept: Physical Properties of Carboxylic Acids
Give a simple chemical test to distinguish between Aniline and N, N-dimethylaniline
Concept: Amines >> Chemical Reactions of Amines - Carbylamine Reaction
