A radioactive element emits 200 particles per second. After three hours 25 particles per second are emitted. The half life period of element will be
|
(a) 50 minutes |
(b) 60 minutes |
(c) 70 minutes |
(d) 80 minutes |
(b) 60 minutes
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Assertion : A double convex lens (m = 1.5) has focal length 10 cm. When the lens is immersed in water (m = 4/3) its focal length becomes 40 cm.
Reason : 
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(a) If both assertion and reason are true and the reason is the correct explanation of the assertion. |
|
(b) If both assertion and reason are true but reason is not the correct explanation of the assertion. |
|
(c) If assertion is true but reason is false. |
|
(d) If the assertion and reason both are false. |
There are 
photons of frequency 
in a beam of light. In an equally energetic beam, there are 
photons of frequency 
. Then the correct relation is
|
(a) |
(b) |
(c) |
(d) |
The thermo e.m.f. of a thermocouple varies with the temperature θ of the hot junction as 
in volts where the ratio a/b is 700℃. If the cold junction is kept at 0℃, then the neutral temperature is
|
(a) 700℃ |
|
(b) 350℃ |
|
(c) 1400℃ |
|
(d) No neutral temperature is possible for this thermocouple |
The internal resistance of a cell is the resistance of
|
(a) Electrodes of the cell |
(b) Vessel of the cell |
|
(c) Electrolyte used in the cell |
(d) Material used in the cell |
