# Solved papers for NEET Physics Wave Optics / तरंग प्रकाशिकी NEET PYQ-Wave Optics

### done NEET PYQ-Wave Optics Total Questions - 20

• question_answer1) Colours of thin soap bubbles are due to:                                         [AIPMT 1999]

A)
refraction

B)
dispersion

C)
interference

D)
diffraction

• question_answer2) In Young's double slit experiment, the slits are 2 mm apart and are illuminated by photons of two wavelengths ${{\lambda }_{1}}=12000{\AA}$ and ${{\lambda }_{2}}=10000{\AA}$. At what minimum distance from the common central bright fringe on the screen 2 m from the slit will a bright fringe from one interference pattern coincide with a bright fringe from the other?                                                                                                                                          [NEET 2013]

A)
8 mm

B)
6 mm

C)
4 mm

D)
3 mm

• question_answer3)  A parallel beam of fast moving electrons is incident normally on a narrow slit. A fluorescent screen is placed at a large distance from the slit. If the speed of the electrons is increased, then which of the following statements is correct?        [NEET 2013]

A)
Diffraction pattern is not observed on the screen in the case of electrons

B)
The angular width of the central maximum of the diffraction pattern will increase

C)
The angular width of the central maximum will decrease

D)
None of these

• question_answer4) A beam of light of $\lambda =600\,nm$ from a distant source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away. The distance between first dark fringes on either side of the central bright fringe is                                                                                                                                [NEET 2014]

A)
1.2 cm

B)
1.2 cm

C)
2.4 cm

D)
2.4 cm

• question_answer5) In the Young's double-slit experiment, the intensity of light at a point on the screen (where the path difference is $\lambda$) is K, ($\lambda$ being the wavelength of light used). The intensity at a point where the path difference is $\lambda ,/4,$ will be                                                                                                                                    [NEET 2014]

A)
K

B)
K/4

C)
K/2

D)
zero

• question_answer6) For a parallel beam of monochromatic light of wavelength $'\lambda '$ diffraction is produced by a single slit whose width 'a' is of the order of the wavelength of the light. If D is the   distance of the screen from the slit, the width a the of the central maxima will be                                                                                                      [NEET  2015]

A)
$\frac{2\lambda D}{a}$

B)
$\frac{D\lambda }{a}$

C)
$\frac{Da}{\lambda }$

D)
$\frac{2Da}{\lambda }$

• question_answer7) In a double slit experiment, the two slits are 1 mm apart and the screen is placed 1 m away. A monochromatic light of wavelength 500 nm is used. What will be the width of each slit for obtaining ten maxima of double slit within the central maxima of single slit pattern                                                                                                          [NEET  2015]

A)
0.2 mm

B)
0.1 mm

C)
0.5 mm

D)
0.02 mm

• question_answer8) Two slits in Youngs experiment have widths in the ratio 1 : 25. The ratio of intensity at the maxima and minima in the interference pattern $\frac{{{I}_{\max }}}{{{I}_{\min }}}$ is                                               [NEET (Re) 2015]

A)
$\frac{9}{4}$

B)
$\frac{121}{49}$

C)
$\frac{49}{121}$

D)
$\frac{4}{9}$

• question_answer9) At the first minimum adjacent to the central maximum of a single slit diffraction pattern, the phase difference between the Huygens wavelet from the edge of the slit and the wavelet from the midpoint of the slit is           [NEET (Re) 2015]

A)
$\frac{\pi }{4}$radian

B)
$\frac{\pi }{2}$radian

C)
$\pi$ radian

D)
$\frac{\pi }{8}$ radian

• question_answer10) The Young's modulus of steel is twice that of brass. Two wires of same length and of same area of cross-section, one of steel and another of brass are suspended from the same roof. It we want the lower ends of the wires to be at the same level, then the weight added to the steel and brass wires must be in the ratio of                                          [NEET (Re) 2015]

A)
1 : 2

B)
2 : 1

C)
4 : 1

D)
1 : 1

• question_answer11) In a diffraction pattern due to a single slit of width $'a',$ the first minimum is observed at an angle ${{30}^{o}}$ when light of wavelength $5000\text{ }\overset{o}{\mathop{A}}\,$ is incident on the slit. The first secondary maximum is observed at an angle of :                                                                                                [NEET - 2016]

A)
${{\sin }^{-1}}\left( \frac{1}{4} \right)$

B)
${{\sin }^{-1}}\left( \frac{2}{3} \right)$

C)
${{\sin }^{-1}}\left( \frac{1}{2} \right)$

D)
${{\sin }^{-1}}\left( \frac{3}{4} \right)$

• question_answer12)  The intensity at the maximum in a Young's double slit experiment is ${{I}_{0}}$. Distance between two slits is $d=5\lambda ,$ where $\lambda$ the wavelength of light is used in the experiment. What will be the intensity in front of one of the slits on the screen placed at a distance $D=10\text{ }d$?                                                                          [NEET - 2016]

A)
${{I}_{0}}$

B)
$\frac{{{I}_{0}}}{4}$

C)
$\frac{3}{4}{{I}_{0}}$

D)
v

• question_answer13) Two Polaroids ${{P}_{1}}$ and ${{P}_{2}}$ are placed with their axis perpendicular to each other. Unpolarised light  ${{l}_{0}}$ is incident on ${{P}_{1}}$. A third polaroid ${{P}_{3}}$ is kept in between ${{P}_{1}}$ and ${{P}_{2}}$ such that its axis makes an angle ${{45}^{o}}$ with that of ${{P}_{1}}$. The intensity of transmitted light through ${{P}_{2}}$ is                                                                                                 [NEET-2017]

A)
$\frac{{{l}_{0}}}{16}$

B)
$\frac{{{l}_{0}}}{2}$

C)
$\frac{{{l}_{0}}}{4}$

D)
$\frac{{{l}_{0}}}{8}$

• question_answer14)  Youngs double slit experiment is first performed in air and then in a medium other than air. It is found that 8th bright fringe in the medium lies where 5th dark fringe lies in air. The refractive index of the medium is nearly     [NEET-2017]

A)
1.78

B)
1.25

C)
1.59

D)
1.69

• question_answer15) Unpolarised light is incident from air on a plane surface of a material of refractive index $'\mu '$. At a particular angle of incidence 'i', it is found that the reflected and refracted rays are perpendicular to each other. Which of the following options is correct for this situation?                                                                                         [NEET - 2018]

A)
$i={{\sin }^{-1}}\left( \frac{1}{\mu } \right)$

B)
Reflected light is polarised with its electric vector perpendicular to the plane of incidence

C)
Reflected light is polarised with its electric vector parallel to the plane of incidence

D)
$i={{\tan }^{-1}}\left( \frac{1}{\mu } \right)$

• question_answer16) In Young's double slit experiment the separation d between the slits is 2 mm, the wavelength $\lambda$ of the light used is $\text{5896 { }\!\!\mathrm{\AA}\!\!\text{ }}$ and distance D between the screen and slits is 100 cm. It is found that the angular width of the fringes is $\text{0}\text{.20 }\!\!{}^\circ\!\!\text{ }$. To increase the fringe angular width to $\text{0}\text{.21 }\!\!{}^\circ\!\!\text{ }$ (with same $\lambda$ and D) the separation between the slits needs to be changed to                                                                                                            [NEET - 2018]

A)
2.1 mm

B)
1.9 mm

C)
1.8 mm

D)
1.7 mm

• question_answer17) Which colour of the light has the longest wavelength?                                    [NEET 2019]

A)
Green

B)
violet

C)
Red

D)
blue

• question_answer18) In a double slit experiment, when light of wavelength 400 nm was used, the angular width of the first minima formed on a screen placed 1 m away, was found to be $0.2{}^\circ$. What will be the angular width of the first minima. If the entire experimental apparatus is immersed in water? $({{\mu }_{water}}=4/3)$                                    [NEET 2019]

A)
$0.05{}^\circ$

B)
$0.1{}^\circ$

C)
$0.266{}^\circ$

D)
$0.15{}^\circ$

• question_answer19) The Brewsters angle ${{i}_{b}}$ for an interface should be                         [NEET 2020]

A)
$30{}^\circ <{{i}_{b}}<45{}^\circ$

B)
$45{}^\circ <{{i}_{b}}<90{}^\circ$

C)
${{i}_{b}}=90{}^\circ$

D)
$0{}^\circ <{{i}_{b}}<30{}^\circ$

• question_answer20) In Youngs double slit experiment, if the separation between coherent sources is halved and the distance of the screen from the coherent sources is doubled, then the fringe width becomes:                          [NEET 2020]

A)
half

B)
four times

C)
one-fourth

D)
double