Examsnet
Unconfined exams practice
Home
Exams
Banking Entrance Exams
CUET Exam Papers
Defence Exams
Engineering Exams
Finance Entrance Exams
GATE Exam Practice
Insurance Exams
International Exams
JEE Exams
LAW Entrance Exams
MBA Entrance Exams
MCA Entrance Exams
Medical Entrance Exams
Other Entrance Exams
Police Exams
Public Service Commission (PSC)
RRB Entrance Exams
SSC Exams
State Govt Exams
Subjectwise Practice
Teacher Exams
SET Exams(State Eligibility Test)
UPSC Entrance Exams
Aptitude
Algebra and Higher Mathematics
Arithmetic
Commercial Mathematics
Data Based Mathematics
Geometry and Mensuration
Number System and Numeracy
Problem Solving
Board Exams
Andhra
Bihar
CBSE
Gujarat
Haryana
ICSE
Jammu and Kashmir
Karnataka
Kerala
Madhya Pradesh
Maharashtra
Odisha
Tamil Nadu
Telangana
Uttar Pradesh
English
Competitive English
Certifications
Technical
Cloud Tech Certifications
Security Tech Certifications
Management
IT Infrastructure
More
About
Careers
Contact Us
Our Apps
Privacy
Test Index
JEE Main 9 Jan 2019 Shift 2 Solved Paper
Show Para
Hide Para
Share question:
© examsnet.com
Question : 3
Total: 90
At a given instant, say t = 0, two radio active substances A and B have equal activities. The ratio
R
B
R
A
of their activities after time t itself decays with time t as
e
–
3
t
. [f the half-life of A is
m
2
, the half-life of B is :
l
n
2
2
2
l
n
2
l
n
2
4
4
l
n
2
Validate
Solution:
Half life of A =
l
n
2
t
1
2
=
l
n
2
λ
λ
A
= 1
at t = 0 ,
R
A
=
R
B
N
A
e
−
λ
A
T
=
N
B
e
−
λ
B
T
N
A
=
N
B
at t = 0
at t = t
R
B
R
A
=
N
0
e
−
λ
B
t
N
0
e
−
λ
A
t
e
−
(
λ
B
−
λ
A
)
t
=
e
−
t
λ
B
−
λ
A
= 3
λ
B
= 3 +
λ
A
= 4
t
1
2
=
l
n
2
λ
B
=
l
n
2
4
© examsnet.com
Go to Question:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
Prev Question
Next Question
Examsnet