Summary of HC Verma Solutions Part 1 Chapter 20: Dispersion and Spectra
FAQs on HC Verma Solutions Class 11 Chapter 20 - Dispersion and Spectra
1. How do Vedantu's HC Verma Solutions for Chapter 20 help in understanding Dispersion and Spectra?
Vedantu's HC Verma Solutions for Chapter 20 provide detailed, step-by-step explanations for every problem. They focus on clarifying the core concepts, such as dispersive power and the conditions for prism combinations. Instead of just giving the final answer, the solutions demonstrate the correct methodology and reasoning required to solve complex numericals, which is essential for both CBSE exams and competitive tests.
2. What is the correct method to solve problems on the combination of prisms in HC Verma Chapter 20?
To solve problems on prism combinations as per the HC Verma textbook, follow this approach:
First, identify the condition being tested: 'dispersion without deviation' or 'deviation without dispersion'.
For each prism, calculate the angular dispersion (δv - δr) and the mean deviation (δy).
Apply the correct sign convention. If one prism is inverted with respect to the other, its angle and deviations are taken as negative.
Set the net deviation or net dispersion to zero based on the required condition and solve for the unknown variable, such as the angle of the second prism.
3. Why is it important to understand the derivation for 'deviation without dispersion' when solving HC Verma problems?
Simply memorising the formula for deviation without dispersion is insufficient for HC Verma problems. Understanding the derivation is crucial because it clarifies the fundamental principle: the angular dispersion produced by the first prism is completely cancelled by the second. This conceptual clarity helps you tackle modified questions where prisms might be made of different materials or immersed in a liquid, situations where the standard formula might not directly apply.
4. What is a common mistake students make when solving HC Verma questions on dispersive power?
A common mistake is incorrectly calculating the mean deviation. Students often use the refractive index for yellow light (μy) to calculate it. However, if μy is not provided, the correct approach as expected in HC Verma is to approximate the mean deviation by taking the average of the deviations for the extreme colours, i.e., (δv + δr) / 2. Using the wrong value for mean deviation leads to an incorrect value for the dispersive power (ω).
5. How are the concepts of Cauchy's formula applied in the numericals of HC Verma's Chapter 20?
Cauchy's formula (μ = A + B/λ²) establishes that the refractive index (μ) is dependent on the wavelength (λ) of light. In HC Verma's numericals, this principle is key. While you may not need to use the formula directly in calculations, the concept is tested in questions that ask you to compare the deviation or dispersion for different colours. The solutions help clarify that since violet light has a shorter wavelength, its refractive index is higher, causing it to deviate more than red light.
6. How do the HC Verma solutions for Chapter 20 connect the phenomena of dispersion with different types of spectra?
The solutions for this chapter build a bridge between the mechanical act of light splitting through a prism and the resulting spectrum. They explain that calculating angular dispersion is the physical basis for a spectrometer's ability to separate different wavelengths. The problem-solving process helps students understand how a continuous source like the sun produces a continuous spectrum, while an excited gas produces a characteristic line emission spectrum, as each line corresponds to a specific wavelength being dispersed at a unique angle.
7. Beyond formulas, what critical reasoning skills do the HC Verma solutions for Dispersion and Spectra aim to develop?
The solutions for this chapter develop crucial analytical skills beyond rote formula application. They encourage you to:
Visualise the Light Path: Trace how different colours bend at each interface of a prism or a combination of prisms.
Break Down Problems: Analyse a complex system, like a direct-vision spectroscope, by calculating the effects of each component prism separately and then combining them.
Apply Conditions Logically: Understand the 'why' behind conditions like zero net deviation, rather than just using the final equation.
This deepens problem-solving ability for competitive exams like JEE and NEET.
