SECTION-4 : (Maximum Marks : 12)

• This section contains TWO (02) paragraphs.

• Based on each paragraph, there are TWO (02) questions.

• The answer to each question is a NUMERICAL VALUE.

• For each question, enter the correct numerical value of the answer using the mouse and the onscreen virtual numeric keypad in the place designated to enter the answer.

• If the numerical value has more than two decimal places, truncate/round-off the value to TWO decimal places.

• Answer to each question will be evaluated according to the following marking scheme:

Full Marks : +3 If ONLY the correct numerical value is entered in the designated place;

Zero Marks : 0 In all other cases.

PARAGRAPH-I

S 1 and S 1 are two identical sound sources of frequency 656 Hz. The source S 1 is located at O and S 2 moves anti-clockwise with a uniform speed 4 ms -1 on a circular path around O, as shown in the figure. There are three points P, Q and R on this path such that P and R are diametrically opposite while Q is equidistant from them. A sound detector is placed at point P. The source Si can move along direction OP.

[Given: The speed of sound in air is 324 ms -1 ]

When only S 2 is emitting sound and it is Q, the frequency of sound measured by the detector in Hz is__________.