Science (English Medium) कक्षा १२ - CBSE Important Questions

Define the term 'amplitude modulation'

Explain any two factors which justify the need for modulating a low frequency base-band signal.

Draw a schematic sketch showing how amplitude modulated signal is obtained by superposing a modulating signal over a sinusoidal carrier wave.

Explain the term demodulation used in a communication system.

Block diagram of a receiver is shown in the figure:

(a) Identify ‘X’ and ‘Y’.

(b) Write their functions.

In the block diagram of a simple modulator for obtaining an AM signal, shown in the figure, identify the boxes A and B. Write their function.

Distinguish between ‘Analog and Digital signals’.

Examine any six consequences of the disintegration of USSR.

Which one of the following countries was NOT a part of the Soviet Union?

“The ‘Arab Spring’ was the people’s revolution against injustice.” Support the statement with any two examples.

On 19^th March 2003, the US launched its invasion of Iraq the code name ______.

Study the given cartoon carefully and answer the questions that follow: 

1. The soldier shown in the cartoon belongs to which one of the following countries?
   1. USSR
   2. USA
   3. Iraq
   4. Iran
2. In which year was Iraq attacked under the code name ‘Operation Iraqi Freedom'?
   1. 1993
   2. 2000 
   3. 2003
   4. 2008
3. Which one of the following countries shown on the cartoon is a ‘Gulf country’?
   1. Iran
   2. Kazakhstan
   3. Pakistan
   4. Oman
4. The First Gulf War is also known as ______.
   1. Smart War
   2. Operation Liberation
   3. Computer War
   4. Operation Enduring Freedom

The objective of ASEAN is not restricted only to accelerating economic growth. Explain the statement.

Evaluate any three steps taken by the Chinese leadership for the growth of Chinese economy.

Study the given cartoon carefully and answer the questions that follow: 

1. To which country are these two cartoons related?
   1. Japan
   2. Vietnam
   3. South Korea
   4. China
2. Red Book is related to which ideology?
   1. Capitalism
   2. Communism
   3. Humanism
   4. Terrorism
3. What does the 'Red Power Tie' depict?
   1. Negation of communism
   2. Acceptance of Capitalism
   3. Coordination of communism with Capitalism
   4. Negation of Capitalism
4. What is the difference between 'then' and 'now' as per the cartoon?
   1. 'Rigidity' has increased now in the ideology of 'then'.
   2. Rigidity has decreased 'now' in the ideology of 'then'.
   3. The leader under 'then' and the leader under 'now' belong to different political parties.
   4. The leader under 'then' and the leader under 'now' belong to different organisations.

Name any four countries that are included in South Asia.

Highlight the speciality of India-Nepal relations. 

Analyse any three major happenings in Bangladesh that show peoples’ support to democracy.

Assertion (A): During constitutional monarchy in 1990s, the political parties and the common people of Nepal wanted to have a more open and responsive system of government.

Reason (R): The King with the help of the army retained full control over the government and restricted the expansion of democracy in Nepal.

Which one of the following statements about relations between India and Nepal is NOT correct?