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Chapter Overview & SLOs
How is the distance of a reflecting surface calculated from an echo? For echo or SONAR problems, the sound travels a double distance (2d) from source to reflecting surface and back. Therefore, the actual one-way distance is calculated using 2d = v × t, where v is the speed of sound and t is the total round-trip time, so d = v × t / 2.
Example - Echo distance: If a tourist hears an echo after 5 s and the speed of sound is 344 m/s, the total distance traveled is 344 × 5 = 1720 m, so the actual distance to the cliff is 1720/2 = 860 m.
What is the relationship between frequency, speed, and wavelength? The wave equation is v = fλ, where v is wave speed, f is frequency, and λ is wavelength. Rearranged: f = v/λ and λ = v/f.
Example - Frequency in seawater: For sound waves with a speed of 1500 m/s and a wavelength of 45 cm (0.45 m), the frequency is f = 1500/0.45 ≈ 3333.3 Hz.
How do we find the depth of the sea using SONAR? SONAR (Sound Navigation and Ranging) sends an ultrasound pulse and measures the time for the echo to return. Depth d = v × t / 2, where v is speed of sound in seawater (≈ 1500-1550 m/s), t is round-trip time.
Example - SONAR depth: If an ultrasound signal is received back after 5.3 s in seawater (v = 1550 m/s), the depth is d = (1550 × 5.3)/2 = 4107.5 m.
How do we calculate the frequency and period of heartbeats? If a physician counts 69 heartbeats in 1 minute (60 s), frequency f = number of beats / time = 69/60 = 1.15 Hz. Time period T = 1/f = 1/1.15 = 0.8696 s.
What is the relationship between frequency and time period? Frequency f = 1/T, where T is the time period. Time period T = 1/f.
Important unit conversions:
- 1 cm = 0.01 m, so 45 cm = 0.45 m
- 1 minute = 60 seconds
- 1 kHz = 1000 Hz, so 20 kHz = 20,000 Hz
What is the audible wavelength range? For minimum frequency (20 Hz) and maximum frequency (20 kHz = 20,000 Hz), the corresponding wavelengths can be calculated using λ = v/f, where v = 344 m/s (speed of sound in air).
Important note for echo and SONAR problems: Remember the double distance (2d) concept. A common mistake is forgetting to divide the total distance by 2 to find the one-way distance.
These notes are strictly aligned with the Student Learning Outcomes (SLOs) for the FBISE 2026 annual examination.
- How do we calculate the distance of a cliff using an echo? If a tourist hears an echo after 5 s and the speed of sound is 344 m/s, the total distance traveled is 1720 m, making the actual distance to the cliff $d = 1720/2 = 860\text{ m}$.
- How is the frequency of sound in seawater determined? For sound waves with a speed of 1500 m/s and a wavelength of 45 cm (0.45 m), the frequency is calculated as $f = 1500/0.45$, which equals approximately 3333.3 Hz.
- How do we calculate the frequency and period of heartbeats? If a physician counts 69 heartbeats in 1 minute (60 s), the frequency is $69/60 = 1.15\text{ Hz}$, and the time period is $T = 1/1.15 = 0.8696\text{ s}$.
- How do we find the depth of the sea using SONAR? If an ultrasound signal is received back after 5.3 s in seawater ($v = 1550\text{ m/s}$), the depth ($d$) is found by $d = (1550 \times 5.3)/2$, resulting in a depth of 4107.5 m.
Frequently Asked Questions (FAQ)
1. Are these Class 10 Physics notes based on the latest FBISE syllabus for 2026?
Yes, these notes are strictly designed according to the Student Learning Outcomes (SLO) provided by the Federal Board (FBISE) for the 2026 academic year. We regularly update our content to match the latest curriculum changes and exam patterns.
2. Do these Physics 13 notes include solved exercise questions and diagrams?
Absolutely. These notes contain comprehensive solutions to all textbook exercise questions, including Multiple Choice Questions (MCQs), Short Questions, and detailed Long Questions. We also include labeled diagrams and key definitions to help you secure maximum marks in your board exams.
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