WAEC 2018/2019 PHYSICS objective and thoery 
10a) Diffraction refers to various phenomena that occur when a wave encounters an obstacle or a slit. It is defined as the bending of light around the corners of an obstacle or aperture into the region of geometrical shadow of the obstacle. 2 )
i ) quantity of charge
ii) nature of element
iii ) Time
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4a)An intrinsic semiconductor, also called an undoped semiconductoror i-type semiconductor, is a pure semiconductor without any significant dopant species present. The number of charge carriers is therefore determined by the properties of the material itself instead of the amount of impurities.
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7(a). LASER stands for Light Amplification by Stimulated Emission of Radiation.
(b). A laser is a device that emits a beam of coherent light through an optical amplification process.
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10a) Diffraction refers to various phenomena that occur when a wave encounters an obstacle or a slit. It is defined as the bending of light around the corners of an obstacle or aperture into the region of geometrical shadow of the obstacle.
10b)
Critical angle: the angle of incidence beyond which rays of light passing through a denser medium to the surface of a less dense medium are no longer refracted but totally reflected.
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12a)
binding energy is the minimum energy that would be required to disassemble the nucleus of an atom into its component parts. These component parts are neutrons and protons, which are collectively called nucleons.
7(a). LASER stands for Light Amplification by Stimulated Emission of Radiation.
(b). A laser is a device that emits a beam of coherent light through an optical amplification process.
4a)An intrinsic semiconductor, also called an undoped semiconductoror i-type semiconductor, is a pure semiconductor without any significant dopant species present. The number of charge carriers is therefore determined by the properties of the material itself instead of the amount of impurities.
5)
i)They are used In making electric motors
ii)They are used In making radio loud speaker
iii)They are used In making aerial transistors
iv)They are used In making DC dynamo
4a)
Satellite are used for monitoring weather conditions
4b)
i)Rockets are used for space travel
ii)military uses,
iii)launching satellites into space
2)
i)quantity of charge
ii)nature of element
iii)Time
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
6)
Given constant = 2.9×10^-3mk
Temperature = 57degreeC = (57+273)k = 330k
Using landamaxT = constant
landamaxT330 = 2.9×10^-3
landamax = 2.9×10^-3/330
landamax = 8.788×10^-6m
The speed of electromagnetic wave, v = 3×10^8m/s
Using V = f landa
f = v/landa
=3×10^8/8.788×10^-6
=3.4×10^13Hz
(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)
-It is used in production of electricity.
-It is used to study and detect charges in genetic engineering.
-It is used in agriculture.
-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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