1
AIEEE 2009
+4
-1
The surface of a metal is illuminated with the light of $$400$$ $$nm.$$ The kinetic energy of the ejected photoelectrons was found to be $$1.68$$ $$eV.$$ The work function of the metal is : $$\left( {hc = 1240eV.nm} \right)$$
A
$$1.41$$ $$eV$$
B
$$1.51$$ $$eV$$
C
$$1.68$$ $$eV$$
D
$$3.09$$ $$eV$$
2
AIEEE 2008
+4
-1
In an experiment, electrons are made to pass through a narrow slit of width $$'d'$$ comparable to their de Broglie wavelength. They are detected on a screen at a distance $$'D'$$ from the slit (see figure).

Which of the following graphs can be expected to represent the number of electrons $$'N'$$ detected as a function of the detector position $$'y'\left( {y = 0} \right.$$ corresponds to the middle of the slit$$\left. \, \right)$$

A
B
C
D
3
AIEEE 2008
+4
-1
Out of Syllabus
Wave property of electrons implies that they will show diffraction effects. Davisson and Germer demonstrated this by diffracting electrons from crystals. The law governing the diffraction from a crystal is obtained by requiring that electron waves reflected from the planes of atoms in a crystal interfere constructively (see figure).

Electrons accelerated by potential $$V$$ are diffracted from a crystal. If $$d = 1\mathop A\limits^ \circ$$ and $$i = {30^ \circ },\,\,\,V$$ should be about
$$\left( {h = 6.6 \times {{10}^{ - 34}}Js,{m_e} = 9.1 \times {{10}^{ - 31}}kg,\,e = 1.6 \times {{10}^{ - 19}}C} \right)$$

A
$$2000$$ $$V$$
B
$$50$$ $$V$$
C
$$500$$ $$V$$
D
$$1000$$ $$V$$
4
AIEEE 2008
+4
-1
Out of Syllabus
Wave property of electrons implies that they will show diffraction effects. Davisson and Germer demonstrated this by diffracting electrons from crystals. The law governing the diffraction from a crystal is obtained by requiring that electron waves reflected from the planes of atoms in a crystal interfere constructively (see figure).

If a strong diffraction peak is observed when electrons are incident at an angle $$'i'$$ from the normal to the crystal planes with distance $$'d'$$ between them (see figure), de Broglie wavelength $${\lambda _{dB}}$$ of electrons can be calculated by the relationship ($$n$$ is an integer)

A
$$d\,\sin \,i = n{\lambda _{dB}}$$
B
$$2d\,\cos \,i = n{\lambda _{dB}}$$
C
$$2d\,\sin \,i = n{\lambda _{dB}}$$
D
$$d\,\cos \,i = n{\lambda _{dB}}$$
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