Rules to draw ray diagrams & sign convention rules for spherical mirrors

RULES TO DRAW RAY DIAGRAMS FOR SPHERICAL MIRRORS

Rule 1:

The ray passing parallel to principal axis, after reflection passes through focus (or appears to be coming from focus in case of convex mirror)

Rule 2:

The ray passing through Focus (or appears to be passing through focus in case of convex mirror), after reflection becomes parallel to principal axis.

Rule 3:

The ray passing through principal axis comes back in the same path after reflection.

Rule 4:

The ray passing through centre of curvature (or appears to be passing through centre of curvature) comes back in the same path after reflection.

Why the ray comes back in the same path after reflection in Rule 3 & Rule 4?

Because as we know the ray passing through normal to the surface comes back in the same path. So, any ray passing through centre of curvature is passing through normal to the spherical surface as it makes an angle of 90⁰ with the tangent drawn to that point on the surface.

Note: the above rules are used to draw ray diagrams to understand the image formation by spherical mirrors. And the minimum number of rays required to show the formation of image is 2.

In ray optics

Object distance is denoted with ”u”

Image distance is denoted with “v”

Focal length is denoted with “f”

Radius of curvature is denoted with “R”.

Focal length is always half of the radius of curvature f=R/2 (or) R=2f

Sign convention rules for spherical mirrors:

i) All the distances must be measured from pole as pole acts as origin.

ii) The distances measured in the direction of incident rays are taken as positive and the distances measured in opposite direction to incident ray are taken as negative.

iii) The heights measured above principal axis are taken as positive and the heights measured below the principal axis are taken as negative.

thank you

Comments

Potential difference and emf

POTENTIAL DIFFERENCE: When the ends of a conducting wire are connected to the terminals of a battery, an electric field is setup throughout the conductor. This field exerts a force on the charge (electron). Let Fe be the force exerted by the electric field on a free charge q. The free charges accelerate in the direction of the electric field (If the free charges are electrons, then the direction of electric force on them is opposite to the direction of electric field). It means the electric field does some work to move free charges in a specified direction. Let the electric force made the charges move through a distance ‘l’ from A to B as shown in figure . We know that, the work is the product of force and distance along the direction of force. Hence, work done by the electric force on a free charge q is given by W = Fe l [since work is the product of force a...

Ohm's law, resistance and resistivity

OHM’S LAW Before going to Ohm’s law let us discuss in brief about some electrical components or devices we use in electric circuits. A Battery serves as a source of electricity in a circuit. We use mainly two measuring devices in this concept those are Volt meter: used to measure potential difference between the two ends of a conductor. So it is always connected in parallel ( we learn about types of connections later in this chapter) Ammeter: used to measure the current passing in the circuit. So it is always connected in series. Now let us dive in to the activity did by Ohm to understand his concept. Materials required: 5 dry cells of 1.5V each, conducting wires, an ammeter, a volt meter, thin iron spoke of length 10cm, LED and key. Procedure: Connect a circuit as shown in the above figure. Solder the conducting wires to the ends of the iron spoke. Close the key. Note the readings of current from ammeter and potential difference from volt meter in table ...

REFRACTION THROUGH CURVED SURFACES (INTRODUCTION)

BEHAVIOUR OF LIGHT WHEN IT ENTERS FROM ONE MEDIUM TO ANOTHER THROUGH CURVED SURFACES Let us try to understand how to draw ray diagrams in case of curved surfaces. We know that a ray of light passing from rarer to denser medium bends towards normal and bends away to normal when it is passing from denser to rarer medium. So it is important to draw a normal to the curved surface. Any line drawn from centre of curvature to a point on the surface acts like a normal to that surface because it makes an angle of 90 0 with the tangent drawn to that surface. Observe some examples of refraction of light through curved surfaces. Consider blue shaded region as denser medium. 1)1) The ray passing from rarer medium to denser medium bends towards normal. 1)2) The ray passing from denser to rarer medium bends away to normal. 1)3) The ray passing along the normal(through centre of curvature) will not deviate from i...

I WANT PHYSICS

Search This Blog