In an X -ray tube, electrons emitted from a filament (cathode) carrying current I hit a target (anode) at a distance d from the cathode. The target is kept at a potential V higher than the cathode resulting in emission of continuous and characteristic X-rays. If the filament current I is decreased to I 2 , the potential difference V is increased to 2 V , and the separation distance d is reduced to d 2 , then

the cut-off wavelength will reduce to half, and the intensities of all the X-rays will decrease

the cut-off wavelength as well as the wavelengths of the characteristic X-rays will remain the same

the cut-off wavelength will become two times larger, and the intensity of all the X-rays will decrease

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Important Questions on Atoms and Nuclei

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Physics Crash Course JEE Advanced>Chapter 20 - Atoms and Nuclei>Exercise 1>Q 34

Carbon $- 11$ decays to boron $- 11$ according to the following formula: ${}_{6}^{11}C \to {}_{5}^{11}B + e^{+} + v_{e} + 0.96 MeV$ .
Assume that positrons $(e^{+})$ produced in the decay combines with free electrons in the atmosphere and annihilate each other almost immediately. Also, assume that the neutrinos $(v_{e})$ are massless and do not intersect with the environment. At $t = 0$ , we have $1 μ g$ of ${}_{6}^{12}C$ . If the half-life of the decay process is $t_{0}$ , the net energy produced between time, $t = 0$ and $t = 2 t_{0}$ will be nearly,

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Physics Crash Course JEE Advanced>Chapter 20 - Atoms and Nuclei>Exercise 1>Q 35

How soon after the beginning of production of the nuclide will its activity be equal to

A = 1.0 \times 10^{9} dis s^{- 1}

, if a

{}^{32}P

radionuclide with half-life,

T = 14.3 days

is produced in a reactor at a constant rate,

q = 2.7 \times 10^{9} nuclei per second

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Physics Crash Course JEE Advanced>Chapter 20 - Atoms and Nuclei>Exercise 1>Q 36

When

{}_{90}{Th}^{238}

changes into

{}_{83}{Bi}^{222}

, then the number of emitted

α

and

β

particles are

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Physics Crash Course JEE Advanced>Chapter 20 - Atoms and Nuclei>Exercise 1>Q 37

A radioactive sample disintegrates by $10 %$ during one month. How much fraction will disintegrate in four months?

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Physics Crash Course JEE Advanced>Chapter 20 - Atoms and Nuclei>Exercise 1>Q 38

\frac{7}{8}

fraction of a sample disintegrates in $t$ time. How much time it will take to disintegrate

\frac{15}{16}

fraction?

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Physics Crash Course JEE Advanced>Chapter 20 - Atoms and Nuclei>Exercise 1>Q 39

The activity of a sample of radioactive material is

A_{1}

at time

t_{1}

and

A_{2}

at time

t_{2} (t_{2} > t_{1})

. Its mean life is T. Which of the following is correct?

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Physics Crash Course JEE Advanced>Chapter 20 - Atoms and Nuclei>Exercise 1>Q 40

A sample of radioactive material decays simultaneously by two processes

A

and

B

with half lives

\frac{1}{2}

and

\frac{1}{4} hr

, respectively. For first half hour it decays with the process

A,

next one

hr

with the process

B

and for further half an hour with both

A

and

B

. If originally there were

N_{0}

nuclei, find the number of nuclei after

2 hr

of such decay.

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Physics

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Physics Crash Course JEE Advanced>Chapter 20 - Atoms and Nuclei>Exercise 1>Q 41

A radioactive element

X

converts into another stable element

Y

. Half life of

X

2 hrs

. Initially only

X

is present. After time

t

, the ratio of atoms of

X

and

Y

is found to be

1 : 4

, then

t

in hours is

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Important Questions on Atoms and Nuclei

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