Optics Answers

Several monochromatic lights pass through double slits with a separation of s 50 3m. The screen to slits distance is 2.5 m. What is/are the width of its central maximum and its corresponding wavelength(s) where the bright spot can occur? [width is expressed in 3 significant figures]

Wavelength (nm) Width (cm)

A. 350 1.75

B. 400 2.00

C. 575 5.75

D. 700 3.50

A diffraction grating produces a third-order bright spot for wavelength 550 nm at 50^o from the central maximum. What is/are the other angle(s) where the bright spot can occur? [angle is expressed in 2 significant figures]

A. 8^o

B. 18^o

C. 27^o

D. 50^o

A monochromatic light passes through a grating to produce a pattern on a screen at a distance from the grating. Choose the correct statement(s) if the number of lines per com of the grating is doubled.

A. The diffraction pattern becomes brighter.

B. The wavelength of the light becomes longer.

C. The distance between bright fringe increases.

D. The number of observable bright fringes increases

Monochromatic light is incident on double slits. Bright and dark fringes are formed on a screen. If the distance between slits is increased,

A. the central maximum becomes wider.

B. the wavelength becomes shorter.

C. the fringe separation will be increased.

D. the width of each fringe becomes narrower

A beam of monochromatic red light is made to pass through a narrow single slit. Choose the CORRECT statement(s) about the produced diffraction pattern on a screen at a distance from the slit.

A. The centre of the pattern is dark.

B. The centre of the pattern is a bright red.

C. A series of rainbow-like fringes will be produced on the screen.

D. A series of alternating bright red and dark fringes will be produced on the screen.

Diffraction

A. changes the speed of light.

B. causes a wave to spread in space.

C. changes the wavelength of light.

D. occurs only for monochromatic light.

Coherent sources A and B emit electromagnetic waves with a wavelength of 4 cm. The distance between A and B is 16.0 cm. Point P is located somewhere between A and B. Which of the following values is/are the possible distance of P from A, if it is a point of destructive interference?

A. 7 cm

B. 8 cm

C. 9 cm

D. 11 cm

Which statement(s) is/are TRUE about interference effect by a thin film.

A. The effect cannot occur in a vacuum.

B. The effect depends on the thickness of the film.

C. The effect is due to light reflection on both sides of the film.

D. The effect only occurs when the thin film is illuminated using white light.

Two monochromatic sources are said to be coherent if

A. they have the same frequency.

B. they have the same amplitude.

C. they have constant phase relation.

D. the have the same wavelength.

Ahmad has a far point of a mere 50 cm. He uses a contact lens to see the distant object clearly. What is/are the condition(s) about the contact lens?

A. The contact lens is a concave lens.

B. The contact lens is a diverging lens.

C. The focal length of the contact lens is -50 cm.

D. The power of the contact lens is -2.0 D