Atomic Structure Solved Examples | Chemistry for JEE Main & Advanced PDF Download

 Page 1


J E E M a i n s
Q 1 : T h e m a x i m u m n u m b e r o f e l e c t r o n s t h a t c a n h a v e t h e p r i n c i p a l q u a n t u m n u m b e r , n =
3 , a n d s p i n q u a n t u m n u m b e r , m s = - ½ , i s .
( a ) 3
( b ) 7
( c ) 9
( d ) 1 0
A n s : (c)
When n = 3, l = 0, 1, 2 i.e., there are 3s, 3p and 3d orbitals. If all these orbitals are completely
occupied as shown in the figure.
Total 18 electrons, 9 electrons with s = + ½ and 9 with s = -½
Alternatively, in any nth orbit, there can be a maximum of 2n
2
electrons.
Hence, when n = 3, the number of maximum electrons = 18. Out of these 18 electrons, 9 can
have spin -½ and the remaining nine with spin = + ½
 
Q 2 : T h e u n c e r t a i n t y i n t h e p o s i t i o n o f a n e l e c t r o n ( m a s s = 9 . 1 x 1 0
- 2 8
g ) m o v i n g w i t h a
v e l o c i t y o f 3 . 0 x 1 0
4
c m s
- 1
a c c u r a t e u p t o 0 . 0 0 1 % w i l l b e
( U s e i n t h e u n c e r t a i n t y e x p r e s s i o n , w h e r e h = 6 . 6 2 6 x 1 0
- 2 7
e r g - s )
( a ) 1 . 9 2 c m
( b ) 7 . 6 8 c m
( c ) 5 . 7 6 c m
( d ) 3 . 8 4 c m
A n s : (a)
Page 2


J E E M a i n s
Q 1 : T h e m a x i m u m n u m b e r o f e l e c t r o n s t h a t c a n h a v e t h e p r i n c i p a l q u a n t u m n u m b e r , n =
3 , a n d s p i n q u a n t u m n u m b e r , m s = - ½ , i s .
( a ) 3
( b ) 7
( c ) 9
( d ) 1 0
A n s : (c)
When n = 3, l = 0, 1, 2 i.e., there are 3s, 3p and 3d orbitals. If all these orbitals are completely
occupied as shown in the figure.
Total 18 electrons, 9 electrons with s = + ½ and 9 with s = -½
Alternatively, in any nth orbit, there can be a maximum of 2n
2
electrons.
Hence, when n = 3, the number of maximum electrons = 18. Out of these 18 electrons, 9 can
have spin -½ and the remaining nine with spin = + ½
 
Q 2 : T h e u n c e r t a i n t y i n t h e p o s i t i o n o f a n e l e c t r o n ( m a s s = 9 . 1 x 1 0
- 2 8
g ) m o v i n g w i t h a
v e l o c i t y o f 3 . 0 x 1 0
4
c m s
- 1
a c c u r a t e u p t o 0 . 0 0 1 % w i l l b e
( U s e i n t h e u n c e r t a i n t y e x p r e s s i o n , w h e r e h = 6 . 6 2 6 x 1 0
- 2 7
e r g - s )
( a ) 1 . 9 2 c m
( b ) 7 . 6 8 c m
( c ) 5 . 7 6 c m
( d ) 3 . 8 4 c m
A n s : (a)
Q 3 : T h e t o t a l n u m b e r o f e l e c t r o n s p r e s e n t i n a l l t h e p - o r b i t a l s , a l l t h e p - o r b i t a l s a n d a l l t h e
d - o r b i t a l s o f c e s i u m i o n a r e r e s p e c t i v e l y
( a ) 8 , 2 6 , 1 0
( b ) 1 0 , 2 4 , 2 0
( c ) 8 , 2 2 , 2 4
( d ) 1 2 , 2 0 , 2 2
A n s : (b)
(Cs
35
) = 1s
2
,2s
2
, 2p
6
, 3s
2
, 3p
6
, 3d
10
, 4s
2
, 4p
6
, 4d
10
, 5s
2
, 5p
6
, 6s
1
Cs
+
= 1s
2
, 2s
2
, 2p
6
, 3s
2
, 3p
6
, 3d
10
, 4s
2
, 4p
6
,4d
10
, 5s
2
, 5p
6
Total no. of e
-
in s-orbitals =10
Total no. of e
-
in p-ortbitals = 24
Total no. of e
-
in d-ortbitals = 20.
Q 4 : W h i c h o f t h e f o l l o w i n g i s f a l s e r e g a r d i n g B o h r ’ s m o d e l
( a ) I t i n t r o d u c e s t h e i d e a o f s t a t i o n a r y s t a t e s
( b ) I t e x p l a i n s t h e l i n e s p e c t r u m o f h y d r o g e n
( c ) I t g i v e s t h e p r o b a b i l i t y o f t h e e l e c t r o n n e a r t h e n u c l e u s
( d ) I t p r e d i c t s t h a t t h e a n g u l a r m o m e n t u m o f e l e c t r o n i n H - a t o m = n h / 2 p .
A n s : (c)
Bohr's model doesn't say anything about probability of finding an electron near nucleus. It gives
discrete orbitals as locus for finding electrons.
Q 5 : W h i c h q u a n t u m n u m b e r i s n o t r e l a t e d w i t h S c h r ö d i n g e r e q u a t i o n ?
( a ) P r i n c i p a l
( b ) A z i m u t h a l
( c ) M a g n e t i c
( d ) S p i n
A n s : (d)
Schrodinger's equation depends on radius, shape and orbital orientation.So, it depends on n, l,
m.
But it doesn't depend on spin of the electron.
? So Schrodinger's equation is not related spin quantum number.
Q 6 : T h e r a t i o o f d i f f e r e n c e i n w a v e l e n g t h s o f 1
s t
a n d 2
n d
l i n e s o f L y m a n s e r i e s i n H - l i k e
a t o m t o d i f f e r e n c e i n w a v e l e n g t h f o r 2
n d
a n d 3
r d
l i n e s o f s a m e s e r i e s i s :
( a ) 2 . 5 : 1
( b ) 3 . 5 : 1
( c ) 4 . 5 : 1
( d ) 5 . 5 : 1
A n s : (b)
Page 3


J E E M a i n s
Q 1 : T h e m a x i m u m n u m b e r o f e l e c t r o n s t h a t c a n h a v e t h e p r i n c i p a l q u a n t u m n u m b e r , n =
3 , a n d s p i n q u a n t u m n u m b e r , m s = - ½ , i s .
( a ) 3
( b ) 7
( c ) 9
( d ) 1 0
A n s : (c)
When n = 3, l = 0, 1, 2 i.e., there are 3s, 3p and 3d orbitals. If all these orbitals are completely
occupied as shown in the figure.
Total 18 electrons, 9 electrons with s = + ½ and 9 with s = -½
Alternatively, in any nth orbit, there can be a maximum of 2n
2
electrons.
Hence, when n = 3, the number of maximum electrons = 18. Out of these 18 electrons, 9 can
have spin -½ and the remaining nine with spin = + ½
 
Q 2 : T h e u n c e r t a i n t y i n t h e p o s i t i o n o f a n e l e c t r o n ( m a s s = 9 . 1 x 1 0
- 2 8
g ) m o v i n g w i t h a
v e l o c i t y o f 3 . 0 x 1 0
4
c m s
- 1
a c c u r a t e u p t o 0 . 0 0 1 % w i l l b e
( U s e i n t h e u n c e r t a i n t y e x p r e s s i o n , w h e r e h = 6 . 6 2 6 x 1 0
- 2 7
e r g - s )
( a ) 1 . 9 2 c m
( b ) 7 . 6 8 c m
( c ) 5 . 7 6 c m
( d ) 3 . 8 4 c m
A n s : (a)
Q 3 : T h e t o t a l n u m b e r o f e l e c t r o n s p r e s e n t i n a l l t h e p - o r b i t a l s , a l l t h e p - o r b i t a l s a n d a l l t h e
d - o r b i t a l s o f c e s i u m i o n a r e r e s p e c t i v e l y
( a ) 8 , 2 6 , 1 0
( b ) 1 0 , 2 4 , 2 0
( c ) 8 , 2 2 , 2 4
( d ) 1 2 , 2 0 , 2 2
A n s : (b)
(Cs
35
) = 1s
2
,2s
2
, 2p
6
, 3s
2
, 3p
6
, 3d
10
, 4s
2
, 4p
6
, 4d
10
, 5s
2
, 5p
6
, 6s
1
Cs
+
= 1s
2
, 2s
2
, 2p
6
, 3s
2
, 3p
6
, 3d
10
, 4s
2
, 4p
6
,4d
10
, 5s
2
, 5p
6
Total no. of e
-
in s-orbitals =10
Total no. of e
-
in p-ortbitals = 24
Total no. of e
-
in d-ortbitals = 20.
Q 4 : W h i c h o f t h e f o l l o w i n g i s f a l s e r e g a r d i n g B o h r ’ s m o d e l
( a ) I t i n t r o d u c e s t h e i d e a o f s t a t i o n a r y s t a t e s
( b ) I t e x p l a i n s t h e l i n e s p e c t r u m o f h y d r o g e n
( c ) I t g i v e s t h e p r o b a b i l i t y o f t h e e l e c t r o n n e a r t h e n u c l e u s
( d ) I t p r e d i c t s t h a t t h e a n g u l a r m o m e n t u m o f e l e c t r o n i n H - a t o m = n h / 2 p .
A n s : (c)
Bohr's model doesn't say anything about probability of finding an electron near nucleus. It gives
discrete orbitals as locus for finding electrons.
Q 5 : W h i c h q u a n t u m n u m b e r i s n o t r e l a t e d w i t h S c h r ö d i n g e r e q u a t i o n ?
( a ) P r i n c i p a l
( b ) A z i m u t h a l
( c ) M a g n e t i c
( d ) S p i n
A n s : (d)
Schrodinger's equation depends on radius, shape and orbital orientation.So, it depends on n, l,
m.
But it doesn't depend on spin of the electron.
? So Schrodinger's equation is not related spin quantum number.
Q 6 : T h e r a t i o o f d i f f e r e n c e i n w a v e l e n g t h s o f 1
s t
a n d 2
n d
l i n e s o f L y m a n s e r i e s i n H - l i k e
a t o m t o d i f f e r e n c e i n w a v e l e n g t h f o r 2
n d
a n d 3
r d
l i n e s o f s a m e s e r i e s i s :
( a ) 2 . 5 : 1
( b ) 3 . 5 : 1
( c ) 4 . 5 : 1
( d ) 5 . 5 : 1
A n s : (b)
Q 7 : W h i c h c o m b i n a t i o n o f q u a n t u m n u m b e r n , l , m , s f o r t h e e l e c t r o n i n a n a t o m d o e s n o t
p r o v i d e a p e r m i s s i b l e s o l u t i o n o f t h e w a v e e q u a t i o n ?
( a ) 3 , 2 , - 2 , + 1 / 2
( b ) 3 , 3 , 1 , - ½
( c ) 3 , 2 , 1 , + 1 / 2
( d ) 3 , 1 , 1 , - 1 / 2
A n s : (b)
For a permissible solution of n, l, m, s
Q 8 : T h e v a l u e o f ( n
2
+ n
1
) a n d f o r H e
+
i o n i n a t o m i c s p e c t r u m a r e 4 a n d 8 r e s p e c t i v e l y .
T h e w a v e l e n g t h o f e m i t t e d p h o t o n w h e n e l e c t r o n j u m p f r o m n
2
t o n
1
i s
Page 4


J E E M a i n s
Q 1 : T h e m a x i m u m n u m b e r o f e l e c t r o n s t h a t c a n h a v e t h e p r i n c i p a l q u a n t u m n u m b e r , n =
3 , a n d s p i n q u a n t u m n u m b e r , m s = - ½ , i s .
( a ) 3
( b ) 7
( c ) 9
( d ) 1 0
A n s : (c)
When n = 3, l = 0, 1, 2 i.e., there are 3s, 3p and 3d orbitals. If all these orbitals are completely
occupied as shown in the figure.
Total 18 electrons, 9 electrons with s = + ½ and 9 with s = -½
Alternatively, in any nth orbit, there can be a maximum of 2n
2
electrons.
Hence, when n = 3, the number of maximum electrons = 18. Out of these 18 electrons, 9 can
have spin -½ and the remaining nine with spin = + ½
 
Q 2 : T h e u n c e r t a i n t y i n t h e p o s i t i o n o f a n e l e c t r o n ( m a s s = 9 . 1 x 1 0
- 2 8
g ) m o v i n g w i t h a
v e l o c i t y o f 3 . 0 x 1 0
4
c m s
- 1
a c c u r a t e u p t o 0 . 0 0 1 % w i l l b e
( U s e i n t h e u n c e r t a i n t y e x p r e s s i o n , w h e r e h = 6 . 6 2 6 x 1 0
- 2 7
e r g - s )
( a ) 1 . 9 2 c m
( b ) 7 . 6 8 c m
( c ) 5 . 7 6 c m
( d ) 3 . 8 4 c m
A n s : (a)
Q 3 : T h e t o t a l n u m b e r o f e l e c t r o n s p r e s e n t i n a l l t h e p - o r b i t a l s , a l l t h e p - o r b i t a l s a n d a l l t h e
d - o r b i t a l s o f c e s i u m i o n a r e r e s p e c t i v e l y
( a ) 8 , 2 6 , 1 0
( b ) 1 0 , 2 4 , 2 0
( c ) 8 , 2 2 , 2 4
( d ) 1 2 , 2 0 , 2 2
A n s : (b)
(Cs
35
) = 1s
2
,2s
2
, 2p
6
, 3s
2
, 3p
6
, 3d
10
, 4s
2
, 4p
6
, 4d
10
, 5s
2
, 5p
6
, 6s
1
Cs
+
= 1s
2
, 2s
2
, 2p
6
, 3s
2
, 3p
6
, 3d
10
, 4s
2
, 4p
6
,4d
10
, 5s
2
, 5p
6
Total no. of e
-
in s-orbitals =10
Total no. of e
-
in p-ortbitals = 24
Total no. of e
-
in d-ortbitals = 20.
Q 4 : W h i c h o f t h e f o l l o w i n g i s f a l s e r e g a r d i n g B o h r ’ s m o d e l
( a ) I t i n t r o d u c e s t h e i d e a o f s t a t i o n a r y s t a t e s
( b ) I t e x p l a i n s t h e l i n e s p e c t r u m o f h y d r o g e n
( c ) I t g i v e s t h e p r o b a b i l i t y o f t h e e l e c t r o n n e a r t h e n u c l e u s
( d ) I t p r e d i c t s t h a t t h e a n g u l a r m o m e n t u m o f e l e c t r o n i n H - a t o m = n h / 2 p .
A n s : (c)
Bohr's model doesn't say anything about probability of finding an electron near nucleus. It gives
discrete orbitals as locus for finding electrons.
Q 5 : W h i c h q u a n t u m n u m b e r i s n o t r e l a t e d w i t h S c h r ö d i n g e r e q u a t i o n ?
( a ) P r i n c i p a l
( b ) A z i m u t h a l
( c ) M a g n e t i c
( d ) S p i n
A n s : (d)
Schrodinger's equation depends on radius, shape and orbital orientation.So, it depends on n, l,
m.
But it doesn't depend on spin of the electron.
? So Schrodinger's equation is not related spin quantum number.
Q 6 : T h e r a t i o o f d i f f e r e n c e i n w a v e l e n g t h s o f 1
s t
a n d 2
n d
l i n e s o f L y m a n s e r i e s i n H - l i k e
a t o m t o d i f f e r e n c e i n w a v e l e n g t h f o r 2
n d
a n d 3
r d
l i n e s o f s a m e s e r i e s i s :
( a ) 2 . 5 : 1
( b ) 3 . 5 : 1
( c ) 4 . 5 : 1
( d ) 5 . 5 : 1
A n s : (b)
Q 7 : W h i c h c o m b i n a t i o n o f q u a n t u m n u m b e r n , l , m , s f o r t h e e l e c t r o n i n a n a t o m d o e s n o t
p r o v i d e a p e r m i s s i b l e s o l u t i o n o f t h e w a v e e q u a t i o n ?
( a ) 3 , 2 , - 2 , + 1 / 2
( b ) 3 , 3 , 1 , - ½
( c ) 3 , 2 , 1 , + 1 / 2
( d ) 3 , 1 , 1 , - 1 / 2
A n s : (b)
For a permissible solution of n, l, m, s
Q 8 : T h e v a l u e o f ( n
2
+ n
1
) a n d f o r H e
+
i o n i n a t o m i c s p e c t r u m a r e 4 a n d 8 r e s p e c t i v e l y .
T h e w a v e l e n g t h o f e m i t t e d p h o t o n w h e n e l e c t r o n j u m p f r o m n
2
t o n
1
i s
( a )
( b )
( c )
( d )
A n s : (c)
n
1
+ n
2
= 4
n
2
2
- n
1
2
= 8
? (n
2
+ n
1
)(n
2
- n
1
) = 8
? n
2
- n
1
= 2
? n
1
= 1
n
2
= 3
Q 9 : T h e w a v e l e n g t h a s s o c i a t e d w i t h a g o l f w e i g h i n g 2 0 0 g a n d m o v i n g a t a s p e e d o f 5
m / h o f t h e o r d e r
( a ) 1 0
- 1 0
m
( b ) 1 0
- 2 0
m
( c ) 1 0
- 3 0
m
( d ) 1 0
- 4 0
m
A n s : (c)
It's in the order of 10
-30
s.
Q 1 0 : T h e l o n g e s t w a v e l e n g t h o f H e
+
i n P a s c h e n s e r i e s i s “ m ” , t h e n s h o r t e s t w a v e l e n g t h
o f B e
+ 3
i n P a s c h e n s e r i e s i s ( i n t e r m s o f m ) :
Page 5


J E E M a i n s
Q 1 : T h e m a x i m u m n u m b e r o f e l e c t r o n s t h a t c a n h a v e t h e p r i n c i p a l q u a n t u m n u m b e r , n =
3 , a n d s p i n q u a n t u m n u m b e r , m s = - ½ , i s .
( a ) 3
( b ) 7
( c ) 9
( d ) 1 0
A n s : (c)
When n = 3, l = 0, 1, 2 i.e., there are 3s, 3p and 3d orbitals. If all these orbitals are completely
occupied as shown in the figure.
Total 18 electrons, 9 electrons with s = + ½ and 9 with s = -½
Alternatively, in any nth orbit, there can be a maximum of 2n
2
electrons.
Hence, when n = 3, the number of maximum electrons = 18. Out of these 18 electrons, 9 can
have spin -½ and the remaining nine with spin = + ½
 
Q 2 : T h e u n c e r t a i n t y i n t h e p o s i t i o n o f a n e l e c t r o n ( m a s s = 9 . 1 x 1 0
- 2 8
g ) m o v i n g w i t h a
v e l o c i t y o f 3 . 0 x 1 0
4
c m s
- 1
a c c u r a t e u p t o 0 . 0 0 1 % w i l l b e
( U s e i n t h e u n c e r t a i n t y e x p r e s s i o n , w h e r e h = 6 . 6 2 6 x 1 0
- 2 7
e r g - s )
( a ) 1 . 9 2 c m
( b ) 7 . 6 8 c m
( c ) 5 . 7 6 c m
( d ) 3 . 8 4 c m
A n s : (a)
Q 3 : T h e t o t a l n u m b e r o f e l e c t r o n s p r e s e n t i n a l l t h e p - o r b i t a l s , a l l t h e p - o r b i t a l s a n d a l l t h e
d - o r b i t a l s o f c e s i u m i o n a r e r e s p e c t i v e l y
( a ) 8 , 2 6 , 1 0
( b ) 1 0 , 2 4 , 2 0
( c ) 8 , 2 2 , 2 4
( d ) 1 2 , 2 0 , 2 2
A n s : (b)
(Cs
35
) = 1s
2
,2s
2
, 2p
6
, 3s
2
, 3p
6
, 3d
10
, 4s
2
, 4p
6
, 4d
10
, 5s
2
, 5p
6
, 6s
1
Cs
+
= 1s
2
, 2s
2
, 2p
6
, 3s
2
, 3p
6
, 3d
10
, 4s
2
, 4p
6
,4d
10
, 5s
2
, 5p
6
Total no. of e
-
in s-orbitals =10
Total no. of e
-
in p-ortbitals = 24
Total no. of e
-
in d-ortbitals = 20.
Q 4 : W h i c h o f t h e f o l l o w i n g i s f a l s e r e g a r d i n g B o h r ’ s m o d e l
( a ) I t i n t r o d u c e s t h e i d e a o f s t a t i o n a r y s t a t e s
( b ) I t e x p l a i n s t h e l i n e s p e c t r u m o f h y d r o g e n
( c ) I t g i v e s t h e p r o b a b i l i t y o f t h e e l e c t r o n n e a r t h e n u c l e u s
( d ) I t p r e d i c t s t h a t t h e a n g u l a r m o m e n t u m o f e l e c t r o n i n H - a t o m = n h / 2 p .
A n s : (c)
Bohr's model doesn't say anything about probability of finding an electron near nucleus. It gives
discrete orbitals as locus for finding electrons.
Q 5 : W h i c h q u a n t u m n u m b e r i s n o t r e l a t e d w i t h S c h r ö d i n g e r e q u a t i o n ?
( a ) P r i n c i p a l
( b ) A z i m u t h a l
( c ) M a g n e t i c
( d ) S p i n
A n s : (d)
Schrodinger's equation depends on radius, shape and orbital orientation.So, it depends on n, l,
m.
But it doesn't depend on spin of the electron.
? So Schrodinger's equation is not related spin quantum number.
Q 6 : T h e r a t i o o f d i f f e r e n c e i n w a v e l e n g t h s o f 1
s t
a n d 2
n d
l i n e s o f L y m a n s e r i e s i n H - l i k e
a t o m t o d i f f e r e n c e i n w a v e l e n g t h f o r 2
n d
a n d 3
r d
l i n e s o f s a m e s e r i e s i s :
( a ) 2 . 5 : 1
( b ) 3 . 5 : 1
( c ) 4 . 5 : 1
( d ) 5 . 5 : 1
A n s : (b)
Q 7 : W h i c h c o m b i n a t i o n o f q u a n t u m n u m b e r n , l , m , s f o r t h e e l e c t r o n i n a n a t o m d o e s n o t
p r o v i d e a p e r m i s s i b l e s o l u t i o n o f t h e w a v e e q u a t i o n ?
( a ) 3 , 2 , - 2 , + 1 / 2
( b ) 3 , 3 , 1 , - ½
( c ) 3 , 2 , 1 , + 1 / 2
( d ) 3 , 1 , 1 , - 1 / 2
A n s : (b)
For a permissible solution of n, l, m, s
Q 8 : T h e v a l u e o f ( n
2
+ n
1
) a n d f o r H e
+
i o n i n a t o m i c s p e c t r u m a r e 4 a n d 8 r e s p e c t i v e l y .
T h e w a v e l e n g t h o f e m i t t e d p h o t o n w h e n e l e c t r o n j u m p f r o m n
2
t o n
1
i s
( a )
( b )
( c )
( d )
A n s : (c)
n
1
+ n
2
= 4
n
2
2
- n
1
2
= 8
? (n
2
+ n
1
)(n
2
- n
1
) = 8
? n
2
- n
1
= 2
? n
1
= 1
n
2
= 3
Q 9 : T h e w a v e l e n g t h a s s o c i a t e d w i t h a g o l f w e i g h i n g 2 0 0 g a n d m o v i n g a t a s p e e d o f 5
m / h o f t h e o r d e r
( a ) 1 0
- 1 0
m
( b ) 1 0
- 2 0
m
( c ) 1 0
- 3 0
m
( d ) 1 0
- 4 0
m
A n s : (c)
It's in the order of 10
-30
s.
Q 1 0 : T h e l o n g e s t w a v e l e n g t h o f H e
+
i n P a s c h e n s e r i e s i s “ m ” , t h e n s h o r t e s t w a v e l e n g t h
o f B e
+ 3
i n P a s c h e n s e r i e s i s ( i n t e r m s o f m ) :
( a )
( b )
( c )
( d )
A n s : (d)
Paschen series ? n
1
= 3
Longest wavelength ? 3 ? 4, Shortest 3 ? 8
Q 1 1 : E l e c t r o m a g n e t i c r a d i a t i o n s h a v i n g ? = 3 1 0 Å a r e s u b j e c t e d t o a m e t a l s h e e t h a v i n g
w o r k f u n c t i o n = 1 2 . 8 e V . W h a t w i l l b e t h e v e l o c i t y o f p h o t o e l e c t r o n s w i t h m a x i m u m
K i n e t i c e n e r g y
( a ) 0 , n o e m i s s i o n w i l l o c c u r
( b ) 2 . 1 5 × 1 0
6
m / s
( c ) 2 . 1 8 v 2 × 1 0
6
m / s
( d ) 8 . 7 2 × 1 0
6
m / s
A n s : (c)
Energy of photon