1
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
$$1000$$ $$V$$
2
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
$$d\,\cos \,i = n{\lambda _{dB}}$$
3
AIEEE 2007
+4
-1
Photon of frequency $$v$$ has a momentum associated with it. If $$c$$ is the velocity of light, the momentum is
A
$$hv/c$$
B
$$v/c$$
C
$$h$$ $$v$$ $$c$$
D
$$hv/{c^2}$$
4
AIEEE 2006
+4
-1
The threshold frequency for a metallic surface corresponds to an energy of $$6.2$$ $$eV$$ and the stopping potential for a radiation incident on this surface is $$5V.$$ The incident radiation lies in
A
ultra-violet region
B
infra-red region
C
visible region
D
$$x$$-ray region
EXAM MAP
Medical
NEET