Conceptual Questions for Class 12 Physics Chapter 11 Dual Nature of Radiation and Matter

In this article, we are covering conceptual questions for class 12 Physics Chapter 11 Dual Nature of Matter and Radiation.

Q.1. What happens to the wavelength of a photon after it collides with an electron?

Solution. A photon transfers a part of its energy to the colliding electron, so its energy decreases and consequently wavelength increases.

Q.2. Why are alkali metals most suited as photo-sensitive metals?

Solution. Alkali metals have low work function. Even visible radiation can eject out electrons from them. So alkali metals are most suitable photo-sensitive metals. •

Q.3. In the wave picture of light, intensity of light is determined by square of the amplitude of wave. What determines the intensity of light in the photon picture of light?

Solution. In photon picture, intensity represents number of photons incident per unit area per unit time.

Q.4. For a monochromatic radiation incident on a photosensitive surface, why do all photoelectrons not come out with the same energy? Give reason for your answer.

Solution. The different electrons belong to different energy levels in the conduction band. They need different energies to come out of the metal surface. For the same incident radiation, electrons knocked off from different energy levels come out with different energies.

Q.5. Does each incident photon essentially eject an electron?

Solution. No, it may be absorbed in some other manner. Only about 1% of incident photons are capable of ejecting out electrons.

Q.6. Is photoelectric emission possible at all frequencies? Give reason for your answer.

Solution. No. Photoelectric emission is possible only if the energy of the incident photon is greater than the work function (W₀ = hv₀) of the metal. Hence, the frequency v of the incident radiation must be greater than the threshold frequency v₀.

Q.7. Out of microwaves, ultraviolet rays and infra-red rays, which radiations will be most effective for emission of electrons from a metallic surface?

Solution. Ultraviolet rays are most effective for photoelectric emission because they have highest frequency and hence most energetic.

Q.8. Two beams, one of red light and the other of blue light, of the same intensity are incident on a metallic surface to emit photoelectrons. Which one of the two beams emits electrons of greater kinetic energy?

Solution. Blue light emits electrons of greater kinetic energy because its frequency is higher than that of red light.

Q.9. Why are de-Broglie waves associated with a moving football not visible?

Solution. Due to the large mass of a football, the de- Broglie wavelength (λ = h / mv) associated with a moving football is very small, quite beyond measurement. Hence its wave nature is not visible.

Q.10. Do all the photons have same mass? If not, why?

Mass of a photon = E/c² = hv/c²

Different radiations have different frequencies. So, their photons will have different masses.

Importance of conceptual questions for class 12 physics

Conceptual questions are of utmost importance in Class 12 Physics for several reasons. These questions focus on understanding the fundamental principles and concepts rather than just rote memorization of equations and formulas. Here are some reasons why conceptual questions are crucial in Class 12 Physics:

Deep understanding: Conceptual questions require students to grasp the underlying principles and theories behind physical phenomena. This leads to a deeper understanding of the subject, making it easier to apply the knowledge to various problem-solving scenarios.
Critical thinking: When students tackle conceptual questions, they are encouraged to think critically and analytically. These questions often involve complex scenarios that demand logical reasoning and creative thinking to arrive at the right answers.
Problem-solving skills: Conceptual questions challenge students to solve unfamiliar and intricate problems. As a result, their problem-solving skills are honed, preparing them to tackle more advanced scientific challenges in the future.
Application of concepts: By answering conceptual questions, students learn to apply theoretical concepts to practical situations. This bridges the gap between theory and real-world applications, fostering a holistic understanding of Physics.
Better exam preparation: Class 12 board exams and competitive entrance exams often include conceptual questions. Preparing for such questions not only improves performance in exams but also sets a strong foundation for further studies in physics-related fields.
Enhanced retention: Understanding concepts leads to better retention of knowledge. Unlike rote memorization, conceptual understanding stays with students for a long time, making it easier to build on that knowledge in the future.
Encouraging curiosity: Conceptual questions often pique students’ curiosity and encourage them to explore the subject further. This can spark an interest in Physics as a whole, leading to a lifelong passion for the subject.
Formulating connections: Conceptual questions help students make connections between different topics and subfields within Physics. This interconnected knowledge is essential for a comprehensive understanding of the subject.
Learning from mistakes: When students attempt conceptual questions, they may make mistakes. However, these mistakes provide valuable learning opportunities, as they highlight areas that need further clarification and understanding.
Building confidence: Successfully answering conceptual questions gives students a sense of accomplishment and boosts their confidence in their Physics abilities.

Conceptual Questions for Class 12 Physics Chapter 11 Dual Nature of Radiation and Matter

Conceptual Questions for Class 12 Physics Chapter 11 Dual Nature of Radiation and Matter

Importance of conceptual questions for class 12 physics

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