Flash light equipped with a new set of batteries, produces bright white light. As the batteries wear out
the light intensity gets reduced with no change in its colour
light colour changes first to yellow and then red with no change in intensity
it stops working suddenly while giving white light
colour changes to red and also intensity gets reduced
If a street light of mass Mis suspended from the end of a uniform rod of length L in different possible patterns as shown in figure, then
pattern A is more sturdy
pattern B is more study
pattern C is more sturdy
all will have same sturdiness
The foil bone has a 14C : 12C ratio, which is [ 1/16 ] of that in a living animal bone. If the half-life time of 14C is 5730 years, then the age of the fossil bone is
11460 years
17190 years
22920 years
45840 years
Which one of the following is a possible nuclear reaction?
C.
According to the conservation of mass number
10 + 4 = 13 + 1
According to conservation of charge number
5 + 2 ≠ 7 + 1
hence (a) is not possible
According to conservation of mass number
93 = 94 - 1
According to conservation of charge number,
239 = 239
Hence (c) is not possible
According to conservation of mass number,
11 + 1 = 12
According to conservation of charge number,
7 + 1 ≠ 6 - 1
Hence (d) is not possible
also satisfies both the conservation of mass number and charge. However, 23Na is a very stable isotope and nuclear reaction will be very difficult. The formation of Pu from Np is well known. It satisfies the conditions of conservations and Np is also very unstable. Therefore (c) is the only correct answer.
If alpha, beta and gamma rays carry same momentum, which has the longest wavelength?
Alpha rays
Beta rays
Gamma rays
None, all have same wavelength
A light emitting diode (LED) has a voltage drop of 2 volt across it and passes a current of 10 mA when it operates with a 6 volt battery through a limiting resistor R. The value of R is
40 kΩ
4 kΩ
200 kΩ
400 kΩ
The minimum potential difference between the base and emitter required to switched a silicon transistor ON is approximately
1 V
3 V
5 V
4.2 V