Answer:
29.38 seconds
Explanation:
Half life, T = 22.07 s
No = 1293
Let N be the number of atoms left after time t
N = 1293 - 779 = 514
By the use of law of radioactivity
Where, λ is the decay constant
λ = 0.6931 / T = 0.6931 / 22.07 = 0.0314 decay per second
so,
take natural log on both the sides
0.9225 = 0.0314 t
t = 29.38 seconds
Explanation:
This difference is because of the difference in arrangement of carbon atoms both graphite and Diamond.
Carbon atoms in graphite are arranged in layered form in an infinite array of layers. These layers are held together by a weaker force of attraction called vander waal's force of attraction such that layer's can slip over one another. Whereas in diamond carbon atoms are arranged tetrahedrally. Each carbon atom is attached to four carbon atoms with a bond angle of 109.5°. It is strong rigid three dimensional structure that results in infinite array atoms. This accounts for hardness of the diamond.
Answer:
beam of light converges to a point A. A lens is placed in the path of the convergent beam 12 cm from P.
To find the point at which the beam converge if the lens is (a) a convex lens of focal length 20 cm, (b) a concave lens of focal length 16 cm
Solution:
As per the given criteria,
the the object is virtual and the image is real (as the lens is placed in the path of the convergent beam)
(a) lens is a convex lens with
focal length, f=20cm
object distance, u=12cm
applying the lens formula, we get
f
1
=
v
1
−
u
1
⟹
v
1
=
f
1
+
u
1
⟹
v
1
=
20
1
+
12
1
⟹
v
1
=
60
3+5
⟹v=7.5cm
Hence the image formed is real, at 7.5cm from the lens on its right side.
(b) lens is a concave lens with
focal length, f=−16cm
object distance, 12cm
applying the lens formula, we get
f
1
=
v
1
−
u
1
⟹
v
1
=
f
1
+
u
1
⟹
v
1
=
−16
1
+
12
1
⟹
v
1
=
48
−3+4
⟹v=48m
Hence the image formed is real, at 48 cm from the lens on the right side.
The answer should be C. In this question
