When there is silence in the classroom , close your eyes and sit quietly. Which sounds in your surroundings can you hear now ?
Prepare a common list of sounds and discuss them.

Suppose you and your friend are on the moon. Will you be able to hear any sound

Observe the garbage collected in the dustbin of you classroom and make a list of the various material in it. Discuss with your teacher, how these materials can be properly disposed off. Can we do the same with the garbage generated in our house? Think about it.

Answer the following questions:Make two sufficiently long, identical tubes out of a cardboard. Arrange them on a table, in front of a wall as shown in figure . Place a clock near the end of one of the tubes and try to hear the ticking of the clock at the end of the other tube by placing your ear there. Adjust the angles of the two tubes till you can hear the sound very clearly Measure the angle of incidence theta_1 and the angle of reflection theta_2 . Try to see if they are related in any way. In the experiment, what will happen if you lift one of the tubes to some height?

Answer the following questions: Read the following sequence of events and answer the questions based on the same. Ranjit saw that the dog sitting by his side had suddenly become alert. In a short time, Ranjit heard footsteps of a man and the stranger approached Ranjit. Rajit now understood why the dog had suddenly become alert. Name some other animals that can hear sound of frequency not audible to human beings.

Try this. i. Try to read a book keeping it very far from your eyes. ii. Try to read a book keeping it very close to your eyes. iii. Try to read a book keeping it at a distance of 25 cm from your eyes. At which time you see the alphabets clearly? Why?

Consider the following statement. When jumping from some height, you should bend your knees as you come to rest instead of keeping your legs stiff. Which of the following relations can be useful in explaining the statement?

Suppose you are listening to an out-door live concert sitting at a distance of 150m from the speakers. Your friend is listening to the live broadcast of the concert in another country and the radio signal has to travel 3000 km. to reach him. Who will hear the music first and what will be the time difference between the two? Velocity of light = 3 xx 10^8m//s and that of sound is 330m//s .

Use your brain power! Can you tell : The names of four fatty acids separated from vegetable oils are given in the table. Identify the number of carbon - carbon double bonds from their structure and molecular formula from the below fatty acids which one when reacts with iodine will make the colour of iodine disappear.