When white light passes through a prism, it splits into its component colours. This phenomenon is called
The dispersion of light is the phenomenon of splitting of a beam of white light into its seven constituent colours when passed through a transparent medium. It was discovered by Isaac Newton in 1666. Newton discovered that light is made up of seven different colours. He passed a beam of sunlight through a glass prism. The glass prism split the light into a band of seven colours on his wall. He called this band of colours the ‘spectrum’. Thus the spectrum is a band of seven colours which is obtained by splitting of white light by a glass prism. The order of colours from the lower end of spectrum is violet (V), indigo (I), blue (B), green (G), yellow (Y), orange (O), and red (R). The sequence of the 7 colours so obtained in a spectrum can be remembered by using the acronym ‘VIBGYOR’.
Quantity which does not changes during refraction is
Frequency is the number of occurrences of a repeating event per unit of time. It is related with sound.
A deviation in the path of a ray of light can be produced
A ray of light is deflected twice in a prism. The sum of these deflections is the deviation angle. When the entrance and exit angles are equal, the deviation angle of a ray passing through a prism will be minimal.
If you want to see your full image then the, minimum size of the plane mirror
In order to see full image of a person, the minimum size of the mirror should be one half the person's height. This is so because, in reflection, the angle of incidence is equal to angle of reflection.
The wavelengths corresponding to violet, yellow and red lights are λv , λy and λr respectively.
The wavelength of red is maximum and the wavelength of violet is minimum.
An object A is placed at a distance d in front of a plane mirror. If one stands directly behind the object at a distance S from the mirror, then the distance of the image.of A from the individual is
A light bulb is placed between two plane mirrors inclined at an angle of 60°. The number of images formed are
Let, the angle of inclination be Theta ° Since the formula is 360 / theta - 1
Mirrors are inclined at an angle of 60°
360/60 - 1 = 5
Therefore, the number of images formed is 5.
A person of height 1.8 standing at the centre of a room having equal dimensions of 10 m wishes to see the full image of the back wall in the mirror fixed on the front wall. The minimum height of the plane mirror needed for this purpose is
The minimum heights needed for this purpose is 10/3m.
Two plane mirrors inclined at an angle to one another have an object placed between them. If five images of the object are observed, the maximum possible angle between the mirrors is
The maximum angle blw the mirror =360/5
In case of a thick plane mirror multiple images arc formed. The brightest of all the images will be
When an object is observed through a thick mirror, silvered at its back, a large number of images are obtained. Out of all the images, the second image is the brightest. In this case, the first image is formed by reflection at the first surface, which is the unsilvered surface of the mirror. The second image is formed after reflection from rear silvered surface, which sends maximum amount of light. Rest of the images formed are due to internal multiple reflections which occur inside the mirror. These images contain lesser amount of light and so their intensity gradually decreases.
Indicate the only correct statement.
The focal length of a concave mirror is f and the distance from the object to the principal focus is x. The magnification obtained will be
In a museum a child walks towards a large concave mirror. He will see that
The magnification of an object placed 10 cm from a convex mirror of radius of curvature 20 cm will be
A concave mirror of focal length 10 cm produces an image five times as large as the object. If the image is in front of the mirror, the distance of the object from the mirror will be
1/f = 1/u +1/ v
-1/10= 1/u +1/5u
To form an image twice the size of the object, using a convex lens of focal length 20 cm, the object distance must be –
To form an image twice the size of the object using a convex lens of focal length 20 cm the object distance must be between 20 cm and 40 cm.
Refractive index of glass w.r.t. air is 3/2. What is the refractie index of air w.r.t glass ?
The mirage is formed due to
A glass prism has refractive index 1.5 and the refracting angle 90° If a ray falls on it at an angle of incidence of 30°, then the angle of emergence will be
If the incident angle is greater than this then there is total internal reflection.
Given , angle of incidence is 300
angle of refraction(r)=48.59°
When monochromatic light passes from vacuum to a material medium and vice versa; which of the following characteristics of light beam does not change ?
A piece of glass when immersed in a transparent solution of refractive index 1.48 becomes almost invisible. The refractive index of glass used is
The refractive index of glass used is 1.48.
Which of the following conditions are necessary for total internal reflection to take place at the boundary of two optical media?
I. Light is passing from optically denser medium to optically rarer medium.
II. Light is passing from optically rarer medium to optically denser medium.
III. Angle of incidence is greater than the critical angle.
IV. Angle of incidence is less than the critical angle.
The speed of light in vacuum is 3.0 × 108 m/s. If the refractive index of a transparent liquid is 4/3, then the speed of light in the liquid is
Given, refractive index of water = 4/3
Speed of light in air = 3 x 10^8
Let, speed of light in water = s
Now, using formula,
Refractive index = speed of light in air/ speed of light in medium(given)
4/3 = 3 x 108 / s
s = 9 x 108 / 4 [cross multiplying]
s = 2.25 x 108 m/sec
The refractive indices of water and glass are 4/3 and 3/2 respectively. The refractive index of water with respect to glass is
Refractive index of water with respect to glass
Which of the following can be used to form a virtual image of an object?
I. convex lens
II. concave lens
III. concave mirror