Skip to main content
Ch 34: Ray Optics
Knight Calc - Physics for Scientists and Engineers 5th Edition
Knight Calc5th EditionPhysics for Scientists and EngineersISBN: 9780137344796Non è quello che usi tu?Cambia libro di testo
Capitolo 34, Problema 3

A student has built a 15-cm-long pinhole camera for a science fair project. She wants to photograph her 180-cm-tall friend and have the image on the film be 5.0 cm high. How far should the front of the camera be from her friend?

Guida verificata passo dopo passo
1
Understand the problem: This is a case of similar triangles formed by the object (the friend) and its image (on the film inside the pinhole camera). The height of the object, the height of the image, and the distances from the pinhole to the object and the image are related proportionally.
Write the relationship for similar triangles: \( \frac{h_{\text{image}}}{h_{\text{object}}} = \frac{d_{\text{image}}}{d_{\text{object}}} \), where \( h_{\text{image}} = 5.0 \ \text{cm} \), \( h_{\text{object}} = 180 \ \text{cm} \), and \( d_{\text{image}} = 15 \ \text{cm} \) (the length of the pinhole camera).
Rearrange the formula to solve for \( d_{\text{object}} \): \( d_{\text{object}} = \frac{d_{\text{image}} \cdot h_{\text{object}}}{h_{\text{image}}} \).
Substitute the known values into the equation: \( d_{\text{object}} = \frac{15 \cdot 180}{5.0} \).
Simplify the expression to find \( d_{\text{object}} \), which represents the distance from the front of the camera to the friend. This will give the required distance.

Risposta video verificata per un problema simile:

Questa soluzione video è stata consigliata dai nostri tutor come utile per risolvere questo problema.

Concetti chiave

Ecco i concetti essenziali che devi comprendere per rispondere correttamente alla domanda.

Similar Triangles

The concept of similar triangles is fundamental in optics, particularly in pinhole cameras. When light rays pass through the pinhole, they create an inverted image on the film. The relationship between the height of the object, the height of the image, and their respective distances from the pinhole can be analyzed using the properties of similar triangles, which states that corresponding angles are equal and the ratios of corresponding sides are proportional.
Video consigliato:
Percorso guidato
01:53
Charges In A Triangle (Rank Force Pairs)

Magnification

Magnification in optics refers to the ratio of the height of the image to the height of the object. It is a crucial concept for understanding how the size of an image changes based on the distance from the object to the camera. In this scenario, the magnification can be calculated using the formula: magnification = height of image / height of object, which helps determine the necessary distance to achieve the desired image size.
Video consigliato:
Percorso guidato
09:03
Mirror Equation

Pinhole Camera Formula

The pinhole camera formula relates the distances of the object and image to the size of the image produced. It can be expressed as: (height of image / height of object) = (distance from pinhole to image / distance from pinhole to object). This formula allows the student to calculate how far the camera should be positioned from her friend to achieve the desired image size, integrating the concepts of similar triangles and magnification.
Video consigliato:
Percorso guidato
06:51
Find Field due to Two Perpendicular Currents