Thin Lenses and Mirrors

What is the primary function of a prism in optics?

To bend light without changing its vergence.

What unit measures the deviation caused by a prism?

Prism diopters (pd or Δ).

What is the apex of a prism?

The thinnest part of the prism.

How does light bend when passing from a medium with a higher refractive index to a lower refractive index?

Away from the normal.

What is the deviation angle (d) in a prism?

The total deviation of the ray.

In which direction does light shift in a prism with the apex pointing downwards?

Towards the base (upwards).

What is the formula for the deviation angle (d) of a prism?

d = i1 + r2 - A.

How are the angles of incidence and refraction related at the first surface of a prism?

They follow Snell's Law.

What is the effect of a prism with a higher index of refraction?

It increases the angle of deviation.

How does a thin prism approximation simplify calculations?

By assuming small apex angles and linear relationships.

What is the formula for the deviation angle (d) in a thin prism approximation?

d = (n - 1) * A.

What is Prentice's Rule?

P = c * F.

How can prisms be used to correct esotropia?

By inducing a base out prism.

How does a Fresnel prism differ from a conventional prism?

It is thinner and flexible.

What is the purpose of a Fresnel prism?

To provide a lightweight and flexible prism solution.

How does a positive lens relate to prisms?

It can be conceptualized as two base-to-base prisms.

How does a negative lens relate to prisms?

It can be conceptualized as two apex-to-apex prisms.

What is the effect of decentering a positive lens upwards?

Base up prism effect.

What is the effect of decentering a negative lens nasally?

Base out prism effect.

How do two prisms BI and BI, in the left and the right eyes respectively, affect each other?

They compound their effects.

How do two prisms BI and BO, in the left and the right eyes respectively, affect each other?

They cancel their effects.

If a prism with a deviation angle (d) of 10° is placed in front of an eye, how will the image be shifted?

Towards the apex by 10°.

What is the primary use of a prism in optometry?

To correct phorias and tropias.

How can a prism be used to correct a visual field defect?

By shifting the image to the area of the functional visual field.

How does the apex angle affect the deviation of light in a prism?

Larger apex angles increase deviation.

How does the index of refraction of a prism material affect the deviation of light?

Higher index increases deviation.

What is the relationship between deviation angle (d) and prism power (P)?

The deviation angle in degrees is directly proportional to the number of prism diopters of a prism.

What type of mirror is used to converge light?

Concave mirror.

What type of mirror is used to diverge light?

Convex mirror.

How does a plane mirror affect the image formed?

The image is virtual, erect, and of the same size as the object.

What is the formula for the focal length (f) of a spherical mirror?

f = R/2.

What is the relationship between object distance (l), image distance (l'), and focal length (f) for a mirror?

1/l + 1/l' = 1/f.

What type of image is formed by a concave mirror when the object is placed beyond the focal point?

Real and inverted.

What type of image is formed by a convex mirror regardless of the object position?

Virtual and erect.

What is the magnification (M) formula for mirrors?

M = L/L'.

What is the primary function of a thin lens?

To refract light and form images.

What is the formula that relates secondary focal length (f) and power in a thin lens?

F=1/f'.

How does a convex lens affect parallel rays of light?

Converges them to a focal point.

How does a concave lens affect parallel rays of light?

Diverges them.

Do thin lenses exist? Why do we study them?

No; Because they are a very useful model that give an approximate solution.

What type of image is formed by a convex lens when the object is placed inside the focal length?

Virtual and erect.

What type of image is formed by a concave lens of a real object?

Virtual and erect.

What is a thick lens?

A lens with significant thickness where the separation between surfaces must be considered.

What is the radius of curvature (r) in lens design?

The distance from the center of curvature to the lens surface.

What is the optical axis of a lens?

The imaginary line passing through the centers of curvature of the lens surfaces.

What is the front vertex focal length (fv) of a thick lens?

The distance from the front surface to the primary focal point.

What is the back vertex focal length (fv) of a thick lens?

The distance from the back surface to the secondary focal point.

How is the equivalent power of a thick lens calculated?

F = F1 + F2 - (t/n) * F1 * F2.

How does increasing the lens thickness of a biconvex lens affects equivalent power?

Thickness decreases the equivalent power.

Thick lenses can be studied as a succession of refractions?

Yes.

What is the effect of a thicker lens on image formation?

It affects both magnification and image distance.

What is the effect of increasing the curvature of a lens surface on its power?

Increases the power.

How does a thick lens differ from a thin lens in terms of optical calculations?

Thick lens requires accounting for lens thickness.

How does a negative meniscus lens affect light?

Diverges light.

How does a positive meniscus lens affect light?

Converges light.

What is the significance of the center of curvature (C) in lens design?

It is the point from which the radius of curvature is measured.

What is the formula for the equivalent power of a thick lens?

Fe​ = F1​+F2​−(n/t​)*F1​F2​.

How does lens thickness affect the optical center (OC) of a thick lens?

It causes a shift in the optical center.

What is the role of the transformation equations in thick lens calculations?

To account for the separation between lens surfaces.

How is the back vertex power (BVP) of a thick lens calculated?

BVP​=F1+F2/(1−(n/t​)F1​F2)​​.

What is the effect of a biconvex lens on light?

Converges light to a point.

What is the effect of a biconcave lens on light?

Diverges light.

What type of image is formed by a thick convex lens if a real object is placed beyond the focal length?

Real and inverted.

What type of image is formed by a thick concave lens regardless of the object position?

Virtual and erect.

How does the index of refraction affect the focal length of a thick lens?

Higher index decreases focal length.

How does a positive meniscus lens differ from a biconvex lens in terms of shape?

Positive meniscus lens has one concave and one convex surface.

What is the formula for calculating the equivalent power (Fe) of a thick lens?

Fe = F1 + F2 - (d/n) * F1 * F2.

How does the radius of curvature affect the power of a thick lens?

Smaller radius increases power.

What is the significance of the principal planes in a thick lens?

They simplify the analysis of complex systems.

How does a biconvex thick lens differ from a biconcave thick lens in terms of image formation of real objects placed further than f?

Biconvex forms real images, biconcave forms virtual images.

What is the role of the center of curvature in determining lens power?

It helps in calculating the radius of curvature.

What is the effect of lens shape on image formation in thick lenses?

Different shapes (e.g., meniscus, biconvex) affect focal length and image position.

How does the separation between lens surfaces in a thick lens affect its optical properties?

It affects both the power and the image distance.

In a mirror...

n'=-n.