Name the system which enables us to locate underwater objects by transmitting ultrasonic waves and detecting the reflecting impulse.

Name the phenomenon which enable us to distinguish between transverse and longitudinal waves?

Name the type of waves which are used for sound ranging.

Name two devices which are used to measure the volume of an object.

Which cells of the retina enable us to see coloured objects around us?

Name three animals who use ultrasonic waves. Explain atleast one animal which uses ultrasonic waves.

Name the technique which is used for detecting presence of pathogens in an organism.

What does the term LOS communication mean? Name the types of waves that are used for this communication. Which of the two height of transmitting antenna and height of receiving antenna can effect the range over which this mode of communication remains effective?

Asnwer the following : (a) Name the em waves which are used for the treatment of certain forms of cancer. Write their frequency range. (b) Thin ozone layer on top of stratosphere is crucial for human survival. Why ? (c) Why is the amount of the momentum transferred by the em waves incident on the surface so small?

To construct a ray diagram we use two rays of light which are so chosen that it is easy to determine their directions after reflection from the mirror. Choose these two ras and state the path of these rays after reflection from a concave mirror . Use these two rays to find the nature and position of the image of an object plced at a distance of 15 cm from a concave mirror of focal length 10 cm.

What do you mean by reflection of sound ? State one condition for the reflecton of a sound wave. Name a device in which reflection of sound wave is used.