Physics – Ans

Physics
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section B answer 3 only

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10a )

Diffraction is the ability of waves to bend around obstacles in their path

10bi)

Critical angle is the highest angle of incidence in a denser medium when angle of refraction in the less dense mediumis 90 degrees

10bii )

Critical angle = 90- 44= 46degrees

The refractive index of the glass is obtained as follows

The refractive index( n )=sini / sinr = sin 46/sin 90= 0 . 7193/ 1

= 0 . 7193

10ci )

fo= 200 Hz

f 1 = 3 v / 4 l => closed pipe

f 1 = v / l => open pipe

but 3 fo= f 1 => closed pipe

3 * 200 = f 1 => f 1 = 600 Hz

Also f 1 = 2 fo=> open pipe

2 fo= 600

fo= 600 / 2 = 300 Hz

10cii )

v = 330 m / s

L =?

fo= 200 Hz

fo= v / 4 l

=> 200 = 330 / 4 l

800 l = 330

l = 330 / 800

l = 0 . 4124m

10ciii )

fo= v / 2 l

fo= 300 Hz

v = 330 m / s

300 = 330 / 2 l

l = 330 / 600

l = 0 . 55m

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9 ai)

i ) Nature of surface

ii) medium of transmission

9 aii )

i ) state or phase of the substance ( i : e solid ,or gas )

ii) temperature of the meduim

9 b )

i ) temperature

ii) specific heat capacity of the body

9 c )

the statement means that the amount of heat energy required to change 1 kg of liquid mercury to gaseous mecury without change in temperature is 2 . 72* 10^ 5 jkg^ – 1

9 di )

Q= MCDSin

V ^ 2 / R t = MCDsin

( 220 )^ 2 * 4 * 60/ 35= M * 4200* ( 100 – 28)

331885. 7 = 302400m

m = 331885. 7 / 302400 = 1 . 098 kg

9 dii )

V ^ 2 / R t = MLv

( 220 )^ 2 * 5 * 60/ 35= 0 . 3 * Lv

414857. 14= 0 . 3 Lv

Lv = 414857. 14/ 0 . 3

Lv = 1382857 . 13JKg ^ – 1

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12a )

This is defined as the amount of energy that must be supplied to a nucleus to completely separate it ‘ s nuclear particles ( nucleons )

12b )

i ) They have short wavelength and high frequency.

ii) They are highly penetrating .

iii ) They travel in straight lines.

iv ) They don’ t require material medium for their propagation .

12c )

i ) It is used in production of electricity .

ii) It is used to study and detect charges in genetic engineering .

iii ) It is used in agriculture .

iv ) It is used in treatment of cancer .

12di )

E = hf – hfo

but f = v / landa

E = v / landa . h – wo

Where wo = hfo = work function

f = frequency

landa = wavelength

Hence

hf = hfo – E

f = hfo – E / h

f = wo – E / h

Recall ; that v = f landa

Therefore f = v / landa = 3 × 10^ 8 / 4 . 5 × 10- 7

= 3 / 4 . 5 × 10^ 8 + 7

= 6 . 6 × 10^ 14Hz

f = 6 . 6 × 10^ 14Hz

12dii )

E = hf

= 6 . 6 × 10^ – 34 × 6 . 6 × 10^ 14Hz

= 43. 56× 10^ – 20J

12diii )

Energy of the photoelectron E = hf – vo

= Energy of incident electron – work function

= 4 . 356 × 10^ – 19J – 3 . 0 × 10^ – 19J

= 1 . 356 × 10^ – 19J

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section A Answer 5 Only

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1 a )

Strain can be defined as the ratio of extension per unit length

Strain = extension / length

1 b )

Strain = extension / length

Let original length = L

Final length = 2 L

Extension = 2 L – L = L

Strain = L / L = 1

strain = change in length / original length

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6 )

Given constant = 2 . 9 × 10^ – 3 mk

Temperature = 57degreeC = ( 57+ 273 ) k = 330 k

Using landamaxT = constant

landamaxT330 = 2 . 9 × 10^ – 3

landamax = 2 . 9 × 10^ – 3 / 330

landamax = 8 . 788 × 10^ – 6 m

The speed of electromagnetic wave, v = 3 × 10^ 8 m / s

Using V = f landa

f = v / landa

= 3 × 10^ 8 / 8 . 788 × 10^ – 6

= 3 . 4 × 10^ 13Hz

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5 )

Range = u ² Sin2 tita / g

At maximum range

Sin2 tita = 1

2 tita = sin ^ – 1 ( 1 )

2 tita = 90dgrees

Tita = 90/ 2 = 45degree

Maximum height reached = u ² sin ² tita / 2 g

= u ² ( sin 45) ² / 2 g

= 200² ( sin 45) ² / 2 ( 10)

= 40000 ( 1 / √2 ) 2 / 20

= 40000 ( 1 / 2 ) / 20

= 20000 / 20

= 1000metres .

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4 a )

An intrinsic semiconductor is an

undoped semiconductor that is a pure semiconductor without any significant dopant

species present .

4 b )

The P Type semiconductor is a type of semiconductor that

carries a positive charge , while the N type semiconductor carries a

negative charge .

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2 )

i ) Silicon Dioxide

ii) Silica Powder

iii ) Germanium Tetrachloride

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3 )

i ) Ferromagnetic material

ii) Diamgentic material

iii ) Pamangentic material

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7 a )

LASER stands for Light Amplification by Stimulated Emission of Radiation .

7 b )

A laser is a device that emits a beam of coherent light through an optical amplification process .

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Completed

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