List of top Questions asked in CBSE CLASS XII

Explain the following observations using Einstein’s photoelectric equation:
(a) Photoelectric emission does not occur from a surface when the frequency of the light incident on it is less than a certain minimum value.
(b) It is the frequency, and not the intensity of the incident light which affects the maximum kinetic energy of the photoelectrons.
(c) The cut-off voltage \( V_0 \) versus frequency \( \nu \) of the incident light curve is a straight line with a slope \( \frac{h}{e} \).
A solution of glucose (molar mass = 180 g mol\(^{-1}\)) in water has a boiling point of 100.20°C. Calculate the freezing point of the same solution. Molal constants for water \(K_f\) and \(K_b\) are 1.86 K kg mol\(^{-1}\) and 0.512 K kg mol\(^{-1}\) respectively.
Write a comprehensive report on Republic Day celebrations held in your school. You are Heena of class XII E, a member of the school magazine editorial board.
Analyse the role of Gandhiji after independence of India.
Sudha, Sudama and Sulochna were partners in a firm sharing profits equally. On 31st March, 2020, Sudha retired. On the date of retirement ₹ 2,40,000 became due to her. Sudama and Sulochana agreed to pay Sudha in four equal yearly instalments plus interest @ 10% p.a. on the unpaid balance starting from 31st March, 2021. The firm closes its books on 31st March every year.
Prepare Sudha’s loan account till it is fully paid.
A wire of resistance \( X \, \Omega \) is gradually stretched till its length becomes twice its original length. If its new resistance becomes 40 \( \Omega \), find the value of \( X \).
The electric field (\( \vec{E} \)) and electric potential (\( V \)) at a point inside a charged hollow metallic sphere are respectively:
Write IUPAC names of the following coordination compounds:
\([ \text{CoCl}_2(\text{en})_2]\text{SO}_4 \)
(ii) \( \text{K}_3[\text{Fe}(\text{C}_2\text{O}_4)_3] \)
(ii) Didentate ligand and Ambidentate ligand

\(\textit{Statement I:}\) In case of non-financial enterprises, payment of interest and dividends are classified as financing activities, whereas receipt of interest and dividends are classified as investing activities. 
\(\textit{Statement II:}\) Investing and financing transactions that require the use of cash or cash equivalents, should be excluded from cash flow statement. 
Choose the correct alternative from the following:

The following question is based on pollination. Study the figures carefully and answer the questions that follow.

  • Give the scientific terms for the processes taking place in Figures A and B respectively.
  • Mention two conditions necessary for the process occurring in Figure B.
  •  
    • [(i)] State one advantage and one disadvantage of the process occurring in Figure B. 
      OR
    • [(ii)] Name one plant where, in some flowers only, the process in Figure B takes place and give the reason responsible for it.
Write two characteristics of equipotential surfaces. A uniform electric field of 50 NC\(^{-1}\) is set up in a region along the \( x \)-axis. If the potential at the origin \( (0, 0) \) is 220 V, find the potential at a point \( (4m, 3m) \).
Find a point \( P \) on the line \( \frac{x + 5}{1} = \frac{y + 3}{4} = \frac{z - 6}{-9} \) such that its distance from point \( Q(2, 4, -1) \) is 7 units. Also, find the equation of the line joining \( P \) and \( Q \).
Describe ‘LPG’ and ‘Gobar Gas’ as strategies used to achieve sustainable development in rural areas.

(a) (i) Import substitution policy, if not applied carefully, can be a double-edged sword for any economy. Do you agree with the given statement? Justify your answer with valid arguments.
(ii) State how multilateral trade is different from bilateral trade.
OR 
(b) 
(i) Discuss briefly, causes and consequences of the tax reforms initiated during economic reforms in India.
(ii) Give one example each of a Navratna and a Maharatna company in the public sector in India.

“Under the British rule, India underwent systematic economic exploitation with its resources and wealth being diverted to Britain.” Justify the given statement with valid explanation.
What shows that Charley was clumsy and absent-minded? (The Third Level)
Find the focal length of the plano-convex lens of refractive index 1.5 and radius of curvature 10 cm when it is immersed in a liquid of refractive index 1.25.

A shop selling electronic items sells smartphones of only three reputed companies A, B, and C because chances of their manufacturing a defective smartphone are only 5%, 4%, and 2% respectively. In his inventory, he has 25% smartphones from company A, 35% smartphones from company B, and 40% smartphones from company C.
A person buys a smartphone from this shop

(ii) What is the probability that this defective smartphone was manufactured by company B?

Convert Ethanal to But-2-enal

The current in a solenoid decreases steadily from 6 mA to 2 mA in 50 ms. If an average emf of 0.4 V is induced, find the self-inductance of the solenoid.

‘बाज़ार में कभी–कभी आवश्यकता ही शोषण का रूप धारण कर लेती है।’ — इस कथन को उदाहरण सहित ‘बाज़ार–दर्शन’ पाठ के आधार पर सिद्ध कीजिए। 
 

A beam of light coming from a distant source is refracted by a spherical glass ball (refractive index 1.5) of radius 15 cm. Draw the ray diagram and obtain the position of the final image formed.
(a) Find the point Q on the line \( \frac{2x + 4}{6} = \frac{y + 1}{2} = \frac{-2z + 6}{-4} \) at a distance of \( \frac{\sqrt{5}}{2} \) from the point \( P(1, 2, 3) \).
A capacitor is charged by a battery to a potential difference \( V \). It is disconnected from the battery and connected across another identical uncharged capacitor. Calculate the ratio of total energy stored in the combination to the initial energy stored in the capacitor.
Find the values of \( a \) for which \( f(x) = x^2 - 2ax + b \) is an increasing function for \( x>0 \).