Question 4876:

The critical angle of glass is \(42^{\circ}\), the approxiffate refractive tho dex of this glass is

A. \(1.50\)
B. \(1.38\)
C. \(1.80\)
D. \(2.30\)

Question 4877:

Second harmonic motion of a string
\(1.5 m\) long fixed at both ends \(80 Hz\).
The speed of transverse wave in the string is

A. \(120 ms\)
B. \(120 m / s\)
C. \(2.12 m / s\)
D. \(102 m / s\)

Question 4878:

The echo produced when a motion is fire from a ship some distance from cliff is heard 2 secontigalculate the distance of the ship (if the velocity of Sound in air \(=330 m / s\) )

A. \(138 m\)
B. \(198 m\)
C. \(275 m\)
D. \(296 m\)

Question 4879:

Which of the following is not an example of a machine?

A. Screw
B. Lever
C. Horizontal plane
D. Pulley

Question 4880:

How long will it take to heat \(3 kg\) of L1't from \(28^{"} C\) in an electnc kettle taking 6Atfem 2 220V supply? (specitic heat capacity ofwater is \(4180 J / k\) )

A. \(2 mins\)
B. \(9 mins\)
C. \(10 mins\)
D. \(20 mins\)