ELECTROMAGNETIC WAVES AND LIGHT

Question 1

ELECTROMAGNETIC
RADIATION AND
SPECTRUM?

Answer 1

Electromagnetic waves
are waves which have
electric and magnetic
fields at right angles to
each other

Question 2

INTERFERENCE IN THIN FILMS – I

Answer 2

Interference effects are commonly observed in thin films.

Question 3

INTERFERENCE IN THIN FILMS – II

Answer 3

Ray 1 undergoes a 180° phase change relative to the incident ray, while Ray 2, reflected from the lower surface, experiences no phase change.

Question 4

INTERFERENCE IN
THIN FILMS – III

Answer 4

Two factors influence interference.
* Possible phase reversals on
reflection
* Differences in travel distance

Question 5

NEWTON’S RINGS?

Answer 5

The air film between the glass surfaces
varies in thickness from zero at the point
of contact to some thickness too

Question 6

RAINBOW?

Answer 6

A ray of light strikes a drop of water in the
atmosphere.

Question 7

RAINBOW – II?

Answer 7

Refraction of sunlight by a spherical
raindrop.
▪ At the back surface, the light is reflected

Question 8

RAINBOW – III?

Answer 8

The formation of a rainbow seen by an
observer standing with the Sun behind
his back

Question 9

BLACKBODY RADIATION?

Answer 9

An object at any temperature (above 2.76 K) emits electromagnetic
radiation. Also called thermal radiation.

Question 10

WIEN’S LAW FOR BLACKBODY RADIATION

Answer 10

The wavelength of peak radiation is inversely proportional to temperature (T); as temperature increases, the peak wavelength shifts to shorter wavelengths.

Question 11

PHOTOELECTRIC EFFECT – I?

Answer 11

This is called the photoelectric effect.
▪ The emitted electrons are called
photoelectrons.

Question 12

PHOTOELECTRIC EFFECT – II?

Answer 12

When light (f  threshold frequency) strikes on metal
surface, photoelectrons are emitted.

Question 13

PHOTOELECTRIC EFFECT – III?

Answer 13

One-to-One interaction between photon and electron

Question 14

BOHR’S MODEL OF ATOMS?

Answer 14

Niels Bohr (1885-1962) contributed to early quantum mechanics and, in 1913, explained atomic spectra by combining classical and non-classical ideas, addressing atomic stability.

Question 15

X-RAY SOURCE
CREATION OF X-RAY SOURCE?

Answer 15

The target has a higher electrical potential than the filament, causing electrons to accelerate between them. Higher-energy electrons are unstable and move to lower energy levels to stabilise the system.