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(solution in the pdf version of the book) Compare the light-gathering powers of a 3-cm-diameter telescope and a \(30-\mathrm{cm}\) telescope.

Short Answer

Expert verified
The 30-cm telescope has 100 times the light-gathering power of the 3-cm telescope.

Step by step solution

01

Understanding Light Gathering Power

The light-gathering power of a telescope is directly proportional to the area of its aperture (i.e., the opening through which light enters the telescope). This area can be calculated using the formula for the area of a circle, which is \( A = \pi r^2 \), where \( r \) is the radius of the circle.
02

Calculate the Radii of the Telescopes

For the 3-cm telescope, the radius \( r_1 = \frac{3}{2} = 1.5 \) cm. For the 30-cm telescope, the radius \( r_2 = \frac{30}{2} = 15 \) cm.
03

Calculate the Area for Each Telescope's Aperture

Calculate the area of the aperture for each telescope using the formula \( A = \pi r^2 \).For the 3-cm telescope: \[ A_1 = \pi (1.5)^2 \approx 7.07 \, \text{cm}^2 \]For the 30-cm telescope:\[ A_2 = \pi (15)^2 \approx 706.86 \, \text{cm}^2 \]
04

Compare the Light-Gathering Power

The light-gathering power is proportional to the area, so compare the two areas to find the ratio of their light-gathering powers.\[\text{Ratio} = \frac{A_2}{A_1} = \frac{706.86}{7.07} = 100\]This indicates that the 30-cm telescope can gather 100 times more light than the 3-cm telescope.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Telescope Aperture
A telescope's aperture plays a crucial role in its ability to gather light. The aperture is simply the diameter of the telescope's main optical component, often a lens or mirror, which captures incoming light. A larger aperture allows more light to enter the telescope, enhancing its ability to detect faint objects in the sky. This is particularly important in astronomy, where observing dim stars, distant galaxies, and other celestial phenomena requires as much light as possible. For example, when comparing a 3-cm diameter telescope with a 30-cm diameter one, the larger telescope's aperture allows it to collect significantly more light, making it more effective for detailed observations.

In summary, the aperture is the entryway for light in a telescope. The difference in aperture size between two telescopes leads to significant differences in their observational power, as one can gather much more light than the other. This principle lies at the core of telescope design and selection for various observational needs.
Area of a Circle
The area of a circle is a fundamental concept that applies when calculating the light-gathering power of telescopes. The formula to determine the area is given by the expression \( A = \pi r^2 \), where \( r \) is the circle's radius.

To find this area within the context of telescope apertures, you must first convert the diameter of the telescope's aperture to a radius. The radius is half the diameter, so for a telescope with a 3-cm diameter, the radius is \( 1.5 \) cm. Following this conversion, plug the radius into the formula to find the area. So, for this 3-cm telescope, its aperture area is \( \pi \times (1.5)^2 \approx 7.07 \text{ cm}^2 \). For a 30-cm telescope, the procedure is the same, yielding an area of roughly \( 706.86 \text{ cm}^2 \).

This formula highlights the difference in light-gathering power since the area of the aperture is key to determining how much light the telescope can collect. A larger area results in more light collection and thus a better ability to perceive faint astronomical objects.
Comparative Analysis in Physics
In physics, comparative analysis is a method used to understand differences and similarities between objects or systems. In the case of telescopes, we compare light-gathering power by looking at their aperture areas. By calculating and comparing the areas of two telescope apertures, we can quantitatively determine which telescope is more powerful. This process involves using the area of a circle formula for each telescope and evaluating their light-gathering ratios.

For instance, by determining that a 30-cm diameter telescope gathers 100 times more light than a 3-cm one, we gain insight into how much more effectively the larger telescope can observe faint objects in the universe. This comparison not only helps in choosing the right telescope for specific astronomical needs but also shows the importance of aperture size in designing telescopes.

Thus, comparative analysis in physics assists in drawing meaningful conclusions from observed data by assessing key differences in fundamental parameters such as aperture size, ultimately guiding decisions in scientific instrumentation and observation.

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