Waves, sound and light

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2 26 Waves, sound and light Ripple tank Whether you are dealing with the wave properties of electromagnetic waves (including light), sound or other types of waves, their behaviour is analogous to the behaviour of waves on a water surface. Water waves have the advantage of being visible and moving so slowly that students can observe the wave phenomena directly. By taking advantage of the optical properties of water waves, they can be enlarged and made visible on a screen. The Ripple tank provides a dramatic demonstration of the general properties of waves and propagation phenomena. 1) Reflection and refraction. By using the linear dipper bar plane parallel waves can be produced. Reflection and refraction of waves can be demonstrated by using appropriate barriers in the water tank. 2) Interference occurs when two point source dippers generate circular waves. The distance between the sources and their frequency can be regulated. 3) The famous double slit experiment: When a plane wave encounters a barrier with two holes, these act like two point source dippers, giving rise to the same interference pattern. 4) The transparent lens cross section is covered by only a shallow layer of water. This decreases the propagation velocity corresponding to an increased index of refraction Ripple Tank

3 Waves, sound and light The ripple tank is shown with the mirror and projection screen in place. By removing these, the wavepattern is projected onto the table top and can be traced on a sheet of paper. 6 7 The included vibrator is our rugged model see next page for details. The complete ripple tank comprises the following individual parts: 1) Stroboscope unit ( ) 2) Power Supply (Eur: /UK: ) 3) Traverse and rods (2) f. strobe ( ) 4) Legs (3) and plate holder (2210,1013) 5) Ripple Tank ( ) 6) Mirror (2210,1011) 7) Projection screen (2210,5093) 8) Vibration Generator ( ) 9) Holder for lever arm ( ) 10) Lever Arm w. pivot ( ) 11) Rod with cross foot ( ) 12) Height adjust unit ( ) 13) Cable for vibrator ( ) 14) Remote control f. single pulses ( ) 15) Acrylic block, convex ( ) 16) Acrylic block, concave ( ) 4 17) Acrylic block, prism ( ) 18) Dipper for parallel waves ( ) 19) Pipette flask w. detergent (2210,3190) 20) Accessories in box (2210,0016) Comprises: Single dipper ( ) Double dipper ( ) Barriers, long (2) ( ) Barrier, short ( ) Single dipper tips (5) (2210,2202) Spare pipette ( ) The ripple tank set is supplied in a fibre box segmented for storing the components and with complete user instructions Ripple Tank With the ripple tank you will need a retort stand base like Retort stand base

4 28 Waves, sound and light Vibrator and accessories This vibrator generates powerful mechanical vibrations when used with a signal generator like The rugged construction means years of problem-free use. The unit is fuse protected and supplied with a lock to fix the moving parts while changing accessories. The vibrator is supplied with mounting hardware, a string holder and a spare fuse. Electromechanical vibrator Max. input: 6 V/1A. Dimensions: 120 mm x Ø 100 mm Weight: 1.26 kg Electromechanical Vibrator Chladni plates For use with A thin layer of fine sand is spread over the plate, and resonance patterns ( Chladni figures) can be observed at certain frequencies. The plate resonances are audible Resonance plate, square Resonance plate, circular Sand for Chladni plates

5 Waves, sound and light 29 Flat springs for resonance experiments Various lengths. For use with Fundamental frequencies at 11, 15, 21, 36 and 50 Hz can be readily observed. Interesting standing waves can be seen up to 300 Hz and heard up to 900 Hz Flat Springs for resonance experiments Longitudinal wave spring 155 mm long and 27 mm diameter. Spring constant 4,7 N/m Spiral spring Gas model with piston For use with Steel balls in motion represent gas molecules which lift a plastic piston due to repeated collisions. The model is supplied with piston, balls and a support for placing the apparatus on an overhead projector.. See page Gas model with piston Piano wire ring Used with for demonstrating the relationship between frequency and the number of vibrational nodes. Diameter: 290 mm Piano wire ring Rubber string 2 metres. For use with for demonstrating standing waves Rubber string

6 30 Waves, sound and light Function generator Designed for education In our development team we include experienced physics teachers. This ensures that the technical perfection goes hand in hand with usefulness. For basic use, you just operate two large buttons: One for frequency one for amplitude. That s it. If you want to change waveform or to utilise the new step and sweep modes, the display keeps you updated on the status of the generator. Unique frequency control The frequency is set by a speed sensitive button. Turn slowly to set the display s last digit. Turn faster, and the response accelerates softly. We have designed this function to work intuitively in practical experiments with common physics equipment. Drives speaker, vibrator etc. directly The built-in 10 W power amplifier drives effortlessly powerconsuming appliances as e.g. a vibrator. The amplifier can deliver more than 1 A for all frequencies between Hz and 100 khz and is directly coupled to the generator part - no switches or external cables complicates use. Step mode In many applications you need to study a physical system at a fundamental frequency and at different multiples of this frequency. The special step feature makes this task a breeze. Sweep mode The generator can sweep through a frequency range in order to discover eventual resonances. You decide the frequency range and the speed. You have the choice between a linear sweep (fixed number of Hz per time) and a logarithmic sweep (fixed number of octaves per time). Advanced Features The generator connects to your PC through a standard USB cable and acts as a USB memory stick. Custom defined waveforms (e.g. created by means of a spreadsheet) can be saved to the generator. Sequences of settings can be programmed for automatic execution. Specifications Build-in waveforms Bipolar: Sine, triangle, square Positive: Square pulse, triangle pulse, ramp up, ramp down Distortion (sine): < 0.1 % up to 20 khz; < 1 % otherwise Frequency range 50 Ω and sync outputs: Hz to MHz Power output: Hz to khz Frequency stability: Better than % Amplitude 50 Ω output, no load: 0 to 10 V (20 V p-p for bipolar waveforms) Sync output: 5 V (TTL signal: 0 to 5 V) Power output: 0 to 10 V (20 V p-p for bipolar waveforms) Max current 50 Ω output, short circuit: 200 ma (only briefly) 50 Ω output, into 50 : 100 ma (unlimited) Power output: 1 A (unlimited) Misc. Mains voltage: 230 V; Hz (115 V on request: Item no ) 85 W (max) ; 21 W (idle) Power consumption: Dimensions (W x D x H): 312 x 205 x 117 mm Function generator

7 Waves, sound and light 31 Loudspeaker, small This small loudspeaker approximates a point source of sound. Use two with function generator in experiments with interference of sound waves. Mounted on a 10 mm diameter rod. Power: 1W into 25Ω Dimensions: 165 mm x Ø 67 mm Loudspeaker, small Microphone The small size of this microphone makes it ideal for experiments with sound interference. Other typical applications are measurement of sound frequencies, speed of sound experiments and the recording of sound by data loggers. It is supplied with a one metre cable with a 6 pole, 240 DIN plug which connects directly to the electronic counter type or student timer The microphone can be connected to an oscilloscope or other measuring instruments via type power supply. The frequency range is 20-20,000 Hz. Supplied with Ø 10 mm support rod. Dimensions: 105 mm x Ø 30 mm Microphone without stand Microphone probe Used for measurement of sound pressure levels in locations which are hard to access. The probe is intended for use with resonance tube. Full description on page Microphone probe Loudspeaker This three-way full range speaker system can be used with e.g. the type function generator in the study of sound, frequency, amplitude and timbre. A Ø 10 mm steel rod makes it easy to place the loudspeaker on a stand base like (not included). Frequency range: Hz Power: 50 W into 4 Ω Dimensions: H x W x D: 215 x 116 x 110 mm Loudspeaker Power supply battery box Microphones type are usually powered by a counter or timer. Microphone probe is powered when connected to appropriate datalogging equipment. If these microphones are to be used as stand-alone units (for instance with an oscilloscope), they need external power - which is provided by this battery box. Full description on page Power supply

8 32 Waves, sound and light Resonance tube for sound experiments This resonance tube provides many options for working with sound waves: Examine standing waves in a tube open at both ends, closed at both ends or open at one end and closed at the other. Examine standing waves in a closed tube containing various gasses (e.g. CO 2 ). Vary the length of the half open tube by means of a piston. The apparatus consists of a Plexiglas tube with two end pieces one with a loudspeaker and one with a hole for the piston shaft or for the microphone probe. Cable for the loudspeaker, piston and two mounts are included. (Microphone probe and tripod stand bases are not including). Dimensions: 100 cm x Ø 7 cm Resonance tube R c Standing waves in a closed tube R b t Standing waves in CO 2 R i Standing waves in a tube with open end R o Standing waves in a tube with both ends open R i o o S s Changing the length of the air column. A tuning fork or a loudspeaker can be used as the sound source

9 Waves, sound and light Microphone probe A miniature microphone is mounted at the end of a 740 mm long 8 mm diameter stainless steel probe for measurement of sound pressure levels in locations which are hard to access. The frequency range is 20 to 20,000 Hz. The probe is intended for use with resonance tube. The probe is supplied with a 2 metre cable with a DIN connector. Note: The microphone is powered by an external voltage. This can be provided by our power supply / battery box or by data logging equipment. In order to use the microphone with a multimeter or an oscilloscope the power supply is required Microphone probe Kundt s resonance tube This apparatus is designed for demonstration of standing waves and for determination of the wavelengths of sound waves in air. The tube is supplied with a millimetre scale and a moveable piston for changing the length of the air column. (You will also need an external sound source - e.g Tuning fork 1000 Hz, together with Striking hammer.) Dimensions: 66 cm x Ø 3 cm Kundt s resonance tube Power supply - battery box The power supply is designed for use with microphones and other sensors that require + 5 V DC to operate. (It also makes it possible to use certain combinations of new and old equipment like photo gates and timers for details, refer to the manual available online.) The unit is provided with a battery compartment for 9 V alkaline battery type 6LR61 ( ) which via an electronic regulator supplies the +5 V DC supply voltage for connected probes. The unit has two inputs with 6 pole, 240 DIN connectors and one input with an 8 pole, 270 DIN connector that also accepts a 5 pole, 180 DIN plug. The output terminals comprise two 5 pole, 180 DIN connec- tors and a set of 4 mm safety connectors. Dimensions (L x W x H): 14.3 x 8.4 x 3.7 cm Power supply

10 34 Waves, sound and light Tuning fork, aluminium The large oscillating area of these aluminium tuning forks ensures a good coupling to the surrounding air, making the sound clearly audible. Use one of these in Doppler effect demonstrations by swinging it around in a string. The lengths are 118 and 104 mm, resp. Width: 30 mm Tuning fork, 1700 Hz Tuning fork, 1000 Hz Tuning forks, steel These tuning forks are made of nickel plated steel with the tone and frequency engraved Tuning fork 440 Hz. Length 120 mm Tuning fork 440 Hz. Length 145 mm Pair of tuning forks on resonance boxes The tuning forks are manufactured in special nickel-plated steel. They are used for resonance and dissonance experiments. The resonance boxes are made of lacquered pine and supplied with thick felt pads on the bottom. The set includes a small weight for mounting on one arm of a fork in order to change the frequency. The standard frequency is 440 Hz. Set contains: Two tuning forks + boxes and a hammer Pair of tuning forks on resonance boxes UDGÅR UDGÅR Tuning fork set C-scale, physical The set consists of eight tuning forks from C(256) to C(512) manufactured in nickel plated steel with frequency values engraved. Supplied in carrying case Tuning fork set, C-scale Tuning fork for demonstration experiments It is easy to hear an ordinary tuning fork but somewhat more difficult to show how it moves. The demonstration tuning fork oscillates at a frequency which is far below the audible range (around 5.4 Hz). On the other hand it is easy to observe its motion. Made of nickel plated steel. Length 75 cm Tuning fork for demonstration experiments

11 Waves, sound and light 35 Wave machine The apparatus is used for demonstrating longitudinal and transverse waves. It is supplied with a drive shaft with a crank which acts on a number of vertical rods as it rotates. Each rod has a white marking at the top. Eight of the rods are supplied with an angular extension which makes it possible to observe the corresponding longitudinal wave. A 360 degree scale is mounted at the crank to enable the phase angle to be determined. Dimensions: (L x H x D) 48 x 32x10 cm Wave machine Spiral spring Slinky The migrant spring. Suitable for demonstration of wave motion. Length: 110 mm. Diameter: 75 mm Spiral spring Slinky Spiral spring Slinky This loose, large diameter spring works well on a smooth floor or a large table for demonstration of longitudinal vibrations. Length: 150 mm. Diameter: 75 mm Spiral spring Slinky spring, 3 metres The spring is used for demonstrations of transverse oscillations and for producing standing waves. Large, rugged and easy to see for a large audience. This demonstration spring is ideal for the introduction of the basic concepts of wave motion. Length, unloaded: 300 cm. Diameter: 19 mm Spiral spring, 3 metres

12 36 Waves, sound and light Interference experiments He-Ne laser The laser emits light with a wavelength of nanometres. The emitted light is coherent, i.e. wave fronts propagate in the same phase over a large distance compared with ordinary light sources. The emitted light is highly directional and the beam diameter at the laser is about 0.5 mm increasing very gradually at increasing distances from the laser. The light emitted is not uniformly polarized but changes its polarization at random around the direction of propagation. Light from the laser is ideal for demonstrations of optical interference. If a line grating is placed in the laser beam, the interference pattern will be clearly visible on a projection screen. The laser can be used for a wide range of applications in optics, communication etc He-Ne Laser, max. 1 mw He-Ne Laser, max. 2 mw He-Ne laser, modulated Like but with the option of amplitude modulating the light. The laser is provided with a BNC connector for connection to a function generator, CD-player or similar signal source. For demonstration of optical communication the photodetector is a perfect match. Maximum modulation frequency: 1 MHz He-Ne laser, modulated, max. 1 mw Photodetector The photodetector is provided with a photo diode which generates an electrical signal proportional with the light intensity. The signal can be applied to the built in loudspeaker or used for measurements via the AC and DC output connections. The photodetector can be used for demonstrating communication over a laser beam, fibre optic communication, plotting of interference patterns, etc. The maximum frequency is 1 MHz. The DC signal, proportional to the light intensity, can be monitored by a voltmeter or datalogging equipment Photodetector Laser objective Needed when the laser beam is just too narrow. Together with e.g. an F = 100 mm lens this convex lens is useful for illumination of a larger area of a diffraction grating or a slide with slits. The objective is supplied with a threaded adapter for mounting on the laser s optics adapter Objective 10x achromatic, N.A Cable for photodetector Used to connect the DC output of to e.g. a voltmeter Cable, mini-jack to 2 banana plugs

13 Waves, sound and light 37 Wavelength of light The apparatus is designed to measure the wavelength of light by studying the interference pattern from a double slit. The equipment is well suited for student lab exercises. The device contains a 12 V festoon lamp with a holder for colour filters and a millimetre scale with moveable markers. The light is viewed at a distance of about 3 metres through a double slit. The viewer directs a co-worker to adjust the markers so that the distance between them corresponds to 10 interference maxima. Afterwards the precise distances can be measured and the wavelength of the light can be calculated. Red and blue colour filters and a double slit are provided. Power source required: 12 V AC/DC, 1.3 A Determining wavelength Laser diffraction kit This kit comprises 18 slides which allow performance and demonstration of e.g. Fraunhofer Diffraction, Fresnel Diffraction, a number of other diffraction experiments. Six slides with 1 to 6 slits. Width 0.06 mm, distance 0.20 mm Slide with holes, Diameters mm Three slides with coarse gratings Two slides with fine diffraction gratings (80 and 300 lines per millimetre) Slide with a fine metal gauze (300 mesh) Slide with a tapered single slit Slide with a tapered double slit Two slides with polarizing filters Slide with a transmission hologram The slides are labelled and come in a storage box complete with an inventory list and brief experiment notes Laser Diffraction kit You will find more lasers and accessories in the Optics chapter.

14 38 Waves, sound and light Sound level meter, digital Robust, user friendly sound level meter with 4-digital display. Measuring range from 30 to 130 db divided into three ranges. User can choose dba or dbc weghting. The instrument is provided with a max/min feature and an AC/DC output for connection to a chart recorder or data collection unit. An external 9V DC power supply may be used. Supplied in case with manual, battery and wind shield. Technical Specifications: Ranges: db, db and db Accuracy: +/- 1.5 db Resolution: 0.1 db Frequency range: 31.5 Hz - 8 khz DC output: 10 mv/db, impedance: 50 Ω AC output: 1 V RMS at full scale, impedance: 600 Ω Ω Power supply: 9 V block battery or line adapter Size: 275 x 64 x 30 mm sound level meter, digital