SCIENCE IMPORTANT FORMULAE CLASS - 9
Important Formulae for class 9 science
Updated for new syllabus - 2026
Class 9 science Important Formulae
The Important Science Formulae section at Saraswat Academy provides a complete collection of chapter-wise scientific formulas based on the latest CBSE Syllabus 2026–27. These formulas are carefully selected from the NCERT textbooks and presented in a simple, easy-to-understand format for quick learning and revision. They help students strengthen their conceptual understanding, solve numerical problems accurately, and improve problem-solving speed in Physics, Chemistry, and other formula-based topics. Regular practice of these formulas is essential for homework, class tests, unit tests, practical examinations, half-yearly examinations, annual examinations, and CBSE board examinations. This page serves as a quick revision resource, enabling students to recall important formulas confidently and perform better in both school and competitive examinations.
Regular revision of scientific formulas helps students strengthen conceptual understanding, improve numerical problem-solving skills, and reduce errors in calculations during examinations. Whether you are preparing for school assessments, practical examinations, or CBSE board exams, these chapter-wise science formula sheets provide a quick and effective revision resource. Students are encouraged to practise these formulas alongside NCERT questions, exemplar problems, practical-based questions, competency-based questions, and previous years' board questions to develop scientific reasoning, enhance accuracy, and achieve excellent marks in Science.
Important Formulae: Science Class - 9
Chapter - 10
🧮 Important Formulae
The following are the most important formulae from Chapter 10: Sound Waves – Characteristics and Applications. These formulae are frequently used in numerical problems and examinations.
| Formula | Meaning |
|---|---|
| v = fλ | Speed of Sound = Frequency × Wavelength |
| f = 1/T | Frequency is the reciprocal of the Time Period. |
| T = 1/f | Time Period is the reciprocal of the Frequency. |
| Distance = Speed × Time | Basic formula used to calculate the distance travelled by sound. |
| Time = Distance / Speed | Used to calculate the time taken by sound to travel. |
| Speed = Distance / Time | Used to calculate the speed of sound. |
| Distance by SONAR = (v × t)/2 | Used to find the distance of an underwater object because the sound travels to the object and returns back. |
Important SI Units
| Physical Quantity | SI Unit |
|---|---|
| Speed (v) | metre per second (m/s) |
| Frequency (f) | hertz (Hz) |
| Time Period (T) | second (s) |
| Wavelength (λ) | metre (m) |
| Amplitude (A) | metre (m) |
Formula Summary
| Concept | Formula |
|---|---|
| Speed of Sound | v = fλ |
| Frequency | f = 1/T |
| Time Period | T = 1/f |
| Distance | d = vt |
| Time | t = d/v |
| Speed | v = d/t |
| SONAR Distance | d = (v × t)/2 |
🎯 Exam Formula Box
v = fλ
f = 1/T
T = 1/f
d = vt
v = d/t
d = (v × t)/2 (SONAR)
📌 Remember
- ✔ Frequency and Time Period are inversely proportional.
- ✔ Higher Frequency → Higher Pitch.
- ✔ Greater Amplitude → Louder Sound.
- ✔ In SONAR, divide by 2 because sound travels to the object and returns back.
- ✔ Sound travels fastest in solids, slower in liquids, and slowest in gases.