Physics (Part-ix) (Railway)

When a stick is dipped in water in a container, rays of light from the tip of the stick bend away from the normal as they go from water to air.

• It because of the refraction of light.

The relation between object distance, image distance and focal length of a concave lens is given by the formula 1 / v - 1 / u = 1/f or 1/v = 1/f+ 1/u, where v distance of image from lens, u = distance of object from lens and f = focal length of lens

• So, according to the question l / v = 1/30 + 1/60 = 3/60

• ∴ v = - 20 cm

• A concave lens always forms a virtual, erect, and diminished image between the F and 2F of the lens.

According to Faraday's law of electromagnetic induction, when a conductor moves through a magnetic field, an electric current is induced in it.

• Fleming's left-hand rule is used to find the direction of the force acting on the current carrying conductor placed in a magnetic field.

• It is used in electric motors.

The split ring in the electric motor also known as a commutator reverses the direction of current flowing through the coll after every half rotation of the coil.

• Due to this, the coil continues to rotate in the same direction.

• It is also known as a commutator.

Total distance = f

U = 7/2 f , V = ?

1/f = 1/u = 1/v

⇒ 1/f = 2/7 f * 1/v

⇒ 1/v = 7-2/7 f * 5/7 f

⇒ V = 7 f / 5

Magnificotion = 7/5 f/7 /2 f = 2/5

Now,

m = 1/10

⇒ 2/5 = 1/10

⇒ 1 = 20/5   4 cm

H = I² Rt.

so, heat produced is directly proportional to the square of electric current produced.

The light that bends the least is red colour and the light that bends the maximum is violet colour light.

• Violet colour refracts the most because violet light in the visible light spectrum has a smaller wavelength of about 400 nanometers when compared to red at 650 nanometers.

• During dispersion of white light by a prism, different colors travel with different speed hence they split in prism.

• Red travels the faster while violet travels slowest so Red is on top and violet is at bottom.

Fleming's left-hand rule When a current-carrying conductor is kept in a magnetic field, a force applies on it; the direction of this force can be determined using Fleming's Left-Hand Rule.

• Similarly, if a moving conductor is placed in a magnetic field, an electric current will be induced in it. The direction of the induced current can be determined using Fleming's Right-Hand Rule.

• So, Fleming's left-hand rule describes the direction of force, magnetic field and current at the same instant.

The equation relating the object distance (u), the image distance (v) and lens focal length (f) is called mirror formula.

• 1/f, where u is the Object distance, v is the Image distance, and f is the Focal Length

• It can also be expressed as 1/f = u + v/vu

• ∴ f=uv/u + v

Sign convention is a set of rules to set signs for image distance, object distance, focal length, etc for mathematical analysis of image formation. According to it:

• Height of an object is always considered positive.

• If an image is formed above the principal axis, its height is taken as positive and if below the principal axis then it is taken as negative.