Thin Lenses and Mirrors

What is the primary function of a prism in optics?

To bend light without changing its vergence

What unit is used to measure 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